Reddit mentions of Arris WBM760A Touchstone DOCSIS 3.0 Cable Modem

Yeah, there may be newer models now but here is the modem and router I went with below.

http://www.amazon.com/gp/product/B006UK3K06?psc=1&redirect=true&ref_=oh_aui_search_detailpage

http://www.amazon.com/gp/product/B006QB1RPY?psc=1&redirect=true&ref_=oh_aui_search_detailpage

Doing a quick look your Asus has good reviews, which honestly surprised me as I can't find anything that mentions it having 5GHz or AC wireless. As for your modem it has mixed reviews stating its about 8 years old now and from what you are describing there is a good chance that it needs a Firmware update that might fix the issue but since you don't own it, it's something Comcast would have to do.

Personally, I also have Comcast (Great Lakes region) with download speeds "up to" 75MB and my speed test just pulled 63MB down and 7MB up. I ended up buying my modem so I can lower my bill and I run a Linksys router without issue.

So, long story short, I would try testing your system with a cable right into the modem. Though inconvenient it will let you know if it's your router or modem is the issue. I find it unlikely that it is having a hard time routing the traffic from all your devices and more likely that it's an issue with the modem itself. And as it's a rental you'd have to call Comcast to have them test and either replace it or buy one yourself and then call and have them set it up to their network.

http://www.amazon.com/Arris-WBM760A-Touchstone-DOCSIS-Cable/dp/B006UK3K06/ref=sr_1_1?s=electronics&ie=UTF8&qid=1382638774&sr=1-1&keywords=Arris+WBM760

Arris WBM760A Touchstone DOCSIS 3.0 Cable Modem https://www.amazon.com/dp/B006UK3K06/ref=cm_sw_r_awd_p3tyub1SD92Z1

I got 2 refurbished ones (primary and a spare) from the "amazon warehouse deals" seller for around $30 each with prime shipping. Zero problems with either of them.

Would this one work with comcast as well??

Thanks!
http://www.amazon.com/Arris-WBM760A-Touchstone-DOCSIS-Cable/dp/B006UK3K06/ref=sr_1_6?s=electronics&ie=UTF8&qid=1409255470&sr=1-6&keywords=DOCSIS+3.0