Pair of of Cornwalls for $800? Not bad, depends on condition these go on fleebay for 3-4 times that.
If they are not damaged or need fixing, I think you'd like the sound. They don't need lots of power, so anything with 10-20 watts is enough to power them very loudly.
If you love bass, then you should invest in great sub. Your target budget for sub would heavily depend on your room size. but anything under $500 is nearly junk and good subs start around $800-1000
Brands to go to for sub are: HSU, SVS, Rythmic, plus new Monoprice THX series subs