Reddit mentions of FatMat Self-Adhesive Sound Deadener Pack with Install Kit - 25 Sq Ft x 50 mil Thick

I have a 2012 accord, and the 08-12 have the same body style, so I know what you need and some potential problems you might run into.

You should replace the radio because it'll make a dramatic difference in the sound quality, same with adding an amp. Also, if you want to put quality speakers in, you'll need an amp or you'll risk blowing your speakers.

Problems you'll run into:

• With a new head unit, you'll lose the function of the screen on top, but I think it's a good trade off for the sound quality
  
  
• You can't have speakers in the front doors that are too deep because it'll hit the window, but there are good shallow mount speakers to put there.
  
  
• The back deck WILL rattle, even you you put a good amount of deadener on it, deadener will still help a good amount though. To solve this problem, deaden it, put weather stripping along the back of the deck where it meets the window (I doubled it up where the brake light is back there), and I drilled two small holes from inside the trunk and zip-tied it down around the metal frame under the deck. This worked great for me and I have two 13" subs in a ported box. If you're looking for one 10", it'll definitely work. It might look a little janky, but that's the only way for it to not rattle.
  
  
• To have someone install everything, run the wires, and deaden what you need deadened (which is, at minimum, the front doors and front door panels, rear deck, trunk, trunk lid, and probably the the pillars in the back), you're probably looking at around $300-$600 for about 4-6 hours of work, depending on where you take it to. And some charge more for installing if you didn't buy the parts from them.
  
  In your other post on /r/CarAV, you said you have a couple grand to spend, so I'm going to put a complete SQ system together that you'll be able to keep for a long time and move from car to car.
  
  
• KnuKonceptz 4 gauge amp kit - $50 (they have a cheaper 4 gauge amp kit, but it doesn't have a big enough fuse on it)
  
  
• 100' KnuKonceptz speaker wire - $20
  
  
• RCA cables (need 2 more pairs) - $10 x 2
  
  
• Dash kit - $50
  
  
• Wiring harness - $12
  
• Antenna adapter - $10
  
  
• Steering wheel control interface - $80
  
  
• Kenwood excelon headunit - $260
  
  
• 6.5" Focal component speakers for the front - $250
  
  
• 6.5" JL coax speakers for the back deck - $140
  
  
• Baffles for the speakers on back deck - $8 (you need these if you want to hear these speakers because of noise cancelation from the sub)
  
  
• 10" pioneer sub - $300
  
  
• Crappy pre-fab sub box - $60
  
  
• Custom box for your car - $120 + $15 if you want a grill (They will build it to the specs of the sub, which is 1 cu.ft. sealed if you go with the pioneer)
  
  
• Kenwood excelon 5 channel amp - $500
  
  
• 25ft^2 of sound deadener - $55
  
  
• $1815-1890 + $300-$600 installation + your tax rate
  
  You probably can find some of this stuff cheaper on amazon, but they're not a registered dealer so you're SOL if something goes bad.
  
  I'd go in to the store, get two quotes, 1) just to install all of this stuff you bought online and 2) what it would cost to buy everything from them with installation and see which is cheaper. The cost for dealers on door speakers and subwoofers is literally half of what they sell for, not head units though, they have very little mark up. Chances are the store might end up being cheaper if you tell them exactly what you're looking at online and how much you're planning to spend on it. Win-Win for you and the dealer, he get's business and you get a better price and similar quality products if they can compete with the online prices. Plus you'd be supporting a local business, unless you were planning on going to best buy, car toys, or something like that (don't do that, go to a local place). And if you buy all this stuff from a dealer and have it installed there, if anything goes wrong you can take it back and have them deal with it.
  
  
  
  
  
  

I would start by replacing the factory tweeter with two of these and deadening the doors.

If that doesn't get you where you want to go, you can look into a pair of midbass 6x9 like this.