I want to be able to clearly tell which direction footsteps are coming from in a game.
Based on this alone, I recommend looking at 7.1 setups. That's what I used to use in my old home before I was married, and I was actually spooked a few times because I thought someone was behind me. Certain games take advantage of those features better than others. I specifically remember Metal Gear Solid 4 really taking advantage of the surround sound (PS3 was current gen during that time). Also, since I was single back then, I was able to spend more money on stuff like that, but I really enjoyed it. I still own all of that equipment, but due to room restrictions, I'm currently only using a 3.0 speaker setup which is disappointing.
When I used my 7.1 setup, I had the "front" and "center" channels in their normal locations, and I had my 2 "surround-back" speakers behind me, and my two "surround" speakers on either side of me. It really felt like stuff was moving around me. Sub woofer location typically doesn't matter, but I kept it in front of me to the right of my equipment because I had room there.
