6.1/7.1 isn't really a necessity, IMO. I had a 6.1 setup and when I moved I had to go back to 5.1 - no big deal; still sounds great. Maybe you could use the left over speakers in another room? I'd use the best of the CSW speakers for the surrounds and invest in some good mains.
If <$800 is your budget, you could probably still swing both some speakers and an inexpensive receiver, but it might be pushing it to include a sub too. There are some decent low cost subs that might do the trick, but that will eat into your other components then. At that price point, I'd say $400-500 for the receiver and $300-400 for a good pair of speakers. You might look used for some Def Tech mains to go with your center too, somewhere like
www.audiogon.com
An HTiB at that price point will get you everything, but in most cases, won't sound better than what you could put together yourself over a little time.