I live by myself, in a trailer, so my 42" tv is legs length from the couch, usually have my feet on the lower shelf of the end table it's sitting on, pc right next to it, the other end table, with a smaller tv I plan on hooking up to my comp so I can have the internet open there, love that when I'm playing a game and want to look something up, or if I'm doing any engineering stuff, whatever, comes in handy often. I have the Logitech MK520 wireless keyboard and mouse, my couch cushion works with my mouse, no need for a mouse pad, and the keyboard is right on my lap, unless I'm using my Logitech F310 controller, which looks like a PS controller, but has the Xbox button labels, and a switch on the back to go from one to the other, because some games are setup for Xbox controllers, others PS setup. I want to get
http://gaming.logitech.com/en-us/product/f710-wireless-gamepad so I'm completely wireless. This would still work quite well if I wasn't less than 5 feet from my tv, though if you don't have kids, I'd put the tower next to the couch, so it's easy to power on, and the wireless items are closer, don't know how far they reach, but I'm sure it's at least as far as your typical living room. I also have
http://www.amazon.com/Logitech-X-530-5-1-Speaker-System/dp/B0002WPSCG speakers hooked up to it, so I have full surround sound, though it isn't setup properly, just moved in here a few weeks ago, haven't unpacked half my stuff, but my comp is running like a champ, and I have found a fairly decent way to setup my speakers without bothering to mount them or anything at all lol.
Your tower doesn't have to be very close to your tv at all, HDMI cables can be stupid long, but if you have kids, especially younger ones, then I wouldn't put the tower next to the couch in the open, I'd put it with the entertainment center if possible...
I'm also going to be getting a Logitech G25 or G27 steering wheel, and then I'll be setting up my racing seat also in the living room, but I'll probably have to get another tv for that, though if I get a nice comfy seat from a car, I can game in that, and be able to recline and everything.... Cheaper than a new tv huh? Just have to customize so I have easy access to ash tray, something to hold my keyboard and mouse when not in use, somewhere to set my pop, got some brainstorming to do now. What do you think, leather heated seats?
Probably try to find a standard, but comfy bucket seat from some sports car at the bone yard...