Reddit mentions of KitchenAid KN211WW 11-Wire Whip for 5 and 6 Quart Lift Stand Mixer

I had the same problem when I upgraded to a Pro 600. I then discovered the 11-wire whip, and it's awesome. It will beat two egg whites, no problem. https://www.amazon.com/dp/B000PJ6XGQ/ref=cm_sw_r_cp_apa_fpALzbBH6CK4G

You can also get a beater blade with a rubber edge that scrapes the bowl while mixing.
https://www.amazon.com/dp/B0015TMI28/ref=cm_sw_r_cp_awdb_zuALzbFK7EBAA

If you order either of these, be sure to get the ones that fit your model.

It's pretty fun, because (1) there are endless new toys to acquire (if you're into that!), and (2) it's actually fairly budget-friendly after you get the initial hardware out of the way (ex. KitchenAid mixer etc.)...I mean, a 50-pound sack of flour is like twenty bucks, and you can make a zillion loaves of breads & cookies out of that! I do get a few premium ingredients for specific recipes here & there, but mostly I just use run-of-the-mill ingredients & get really great results!

It's also really fun amping up both the quality of your results & the experiencing of your cooking & baking time. For example, I cook these amazing five-hour carnitas in the oven, which is one of the things that got me into using leaf lard (which then turned into other incredible things, like lard-based oatmeal cookies). But then the off-the-shelf tortillas were disappointing with those stellar carnitas, so I picked up a cast-iron tortilla press (for smashing, not baking!). I then combined that with a lard-based tortilla recipe and oooooh yeah that's an awesome combination of textures, flavors, warmth, and happiness, hahaha! So going down rabbits holes is quite fun with baking!

I do a lot with my 8-cavity mini-loaf pan, which surprisingly freeze well! Banana bread & pumpkin bread with sweet cream cheese spread, cornbread, chocolate chocolate-chip bread, the list is endless! I also bake excellent homemade Twinkies in various flavors on a regular basis. I was never an overly-huge Twinkie fan, but one of my favorite bakeries makes them in a million flavors with a million different fillings & coatings (chocolate-dipped, white-chocolate dipped & dark-chocolate striped, peanut-butter filled chocolate twinkies, raspberry cake coated with coconut, etc.). So endless variations are also quite fun with baking!

If you want to build up your skills on the more technical side, Bigger Bolder Baking is a fantastic website to check out. If you want a few top-notch (I'm talking like "WOW!") recipes to try out right off the bat:

• Chocolate-chip cookies with this specific dark chocolate (only for very special occasions, because $$$)
  
• Glossy fudge brownies with this specific pan ($$$ but will last forever) & this particular cocoa powder ($$$, but the economics actually aren't bad, once you calculate out the price-per-batch, haha!)
  
• Sour-cream pancakes (without blueberries) - great way to test your Danish dough hook!
  
  You'll discover a lot of little tricks over time. For example, which those chocolate-chip cookies above, whipping the cream & sugar & butter & eggs into something that literally resembled whipped cream is a really great trick to know about...most people just stir those together until combined, but they will actually change color, texture, and consistency when whipped long enough! Side note, if you have a KitchenAid, I highly recommend getting a SideSwipe blade (available on Amazon, be sure to get the right blade for your mixer!).
  
  On that topic, I also recommend getting a coated dough hook & an 11-wire whisk. Wait until you try homemade marshmallows! (super easy with that whisk attachment!) When it gets cold out, I cut those bad boys into 2" chunks, skewer them, heat up some water for the delicious Stephen's hot cocoa powder mix, and then torch the marshmallows. That combination came out so good that I started hosting annual hot chocolate parties, lol!
  
  You can get as creative as you want to with baking, too...like with cakes, you can airbrush them, do drip cakes, mirror glaze cakes, you can torch the tops of cupcakes, make cake pops, the list is endless! Depending on what stage you're at in life, especially in my case as a working adult with a family, I don't get a lot of opportunity for creative outlets due to a lack of free time (and energy, tbh lol), but my family has to eat, and baking is a fun way to amp up your enjoyment in life by making cool stuff you can eat & having fun doing it!
  
  Plus pretty much everything is actually really easy, no matter how complicated it looks...you're just following someone else's step-by-step directions, that they have painstakingly figured out for you through probably dozens of iterations to get it perfect (as Stella did when perfecting her lacy brown-butter cookies!), and that mostly boils down to (1) mix stuff in a bowl, (2) bake it, (3) don't burn it, (4) let it cool down & "set". That little four-step process yields amazing no-knead bread, pan pizzas, twinkies, cookies, brownies, you name it!

I used this off brand Metro blade for my KA Pro 600 https://www.amazon.com/BeaterBlade-KA-6L-Metro-Design-KitchenAid/dp/B0015TMI28/ref=sr_1_1?ie=UTF8&qid=1483386039&sr=8-1&keywords=kitchen+aid+pro+600+metro+blade for one year before it broke at the neck/shoulder area. Replaced it with the same blade and that lasted a bit over a year. I don't make bread and the cookies I make are not rock hard. I went looking for a replacement.

Here it is... https://www.amazon.com/KitchenAid-KFE6L-5-5-6-Bowl-Lift-Beater/dp/B006HGZ7AY This one is actually put out by Kitchenaid. I liked the dual silicone edge of the metro, but this blade is stainless steal coated, not plastic like the metro. It is DW safe (I've washed mine at least 25x already. 10/10 would buy again. Well worth the money if you plan on thicker doughs than cake batter.

I also recommend this 11 wire whip attachment (also KA brand) https://www.amazon.com/gp/product/B000PJ6XGQ/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 It is also stainless, unlike the one sold with the mixers, which makes it totally DW safe (have washed that one at least a dozen times since I got it.

IDK if I really answered your questions, but in my experience the KA brand name accessories are worth the money. The quality is markedly different from the off brands, but in the end, it depends on what you are using them for and how much you are using them. The off brands might suit your needs just fine.

Oh, I forgot. I have the meat grinder too. I initially bought the plastic one, but traded up to the ss because of heavy use. Another example of ss being the better choice, though in this case they were both KA brand items.

Good luck to you. As a suggestion, your wife can bake to her heart's content, but have one or two and give away the rest, or the extra 50lbs will be with you in no time. I had to learn the hard way that taking it off was infinitely harder than putting it on. Save yourself and your wife!!

Edit: apologies for the word wall
Edit 2: Make sure you double check your model number before ordering any accessories b/c they may look like they'll fit, but they don't always.