Methinks Leprkon might have caught on to something here...how are you going to run your wires? I have a similar issue in my living room where the only way to run the wires unseen is either up through the attic or under the carpet (I don't have a basement).
If you can go under into a basement, then you might not have much to worry about with the wiring. Go with the inexpensive heavier gage wire like Leprkon suggested, run into down through the walls into the basement, and use some nice looking wallplates with speaker binding posts.
If you don't have a basement, can you run it through the attic? If so, same recommendations except you'll be running wires through the attic instead. If not, then getting either wire or wire covers that match the walls is good. You can also get flat speaker wire that runs along walls and is paintable.
I disagree with Nick regarding a receiver having very little to do with the sound quality. It depends on what else you have in your system and how you're using it. Specifically, the feature set of the receiver may play a large role (or little role if you don't use them). When I went from a Yamaha RX-V992 to my Pioneer VSX-1015TX, there was a huge improvement (to me) in how the system sounded. Not because Pioneer is a better brand than Yamaha, but because the receiver was newer and allowed me to set up more parameters. The Pioneer has auto room set-up that includes some frequency equilization, it has THX modes that I like, and it just sounds less "harsh" than the Yamaha. The Yamaha was fatiguing to listen to on my speakers, while the Pioneer is not. A sound system is basically one large electrical circuit, so it's important to consider every piece of the chain, IMO.
