Welcome, James!
First thing you should do is go audition some speakers at a local store. Conditions are usually not optimal, but that will give you an idea of what sound you like. Just because one ear likes a particular sound does not mean yours will...and it's your money you're spending!

Also need to know the size of the room you're working with to get the best recommendations.
That being said, there's a pretty good deal going on these
http://www.accessories4less.com/cgi-bin/item/CANTLE190BLK
Canton is changing lines and these are the outgoing model. I've not heard them myself, but many have spoken highly of them for about $600/pr
The Athenas I run are also an outgoing model and can be had for about $400/pr
http://www.audioadvisor.com/products.asp?dept=58
Center channels are available for both lines. You should match L/C/R speakers when possible, otherwise you can run into timbre issues. It's not as big an issue with your surrounds.
As for subs, search the sub forum and you'll find that it is not necessary to match your sub to your speakers. Subs and loudspeakers are apples and oranges; often the big speaker brands to not make a quality sub. The big players in the "bang for buck" league are Hsu and SVS. There's also Onix Rocket and Velodyne. All are quality manufacturers. Enjoy!