I have heard of them but will never give someone a recommendation without listening to them first hand.
The speakers I've heard that I'd recommend are:
Bose (JK not in a million years

)
Def Tech
Axiom
SVS
Rockets (if you like a more laid back sound)
Klipsch (you need to listen to a horn though as they are a love hate speaker)
I went with Axiom because of their service and price. A 5.1 system will run you around 1500 bucks and their quality is up there with speakers costing thousands more. This leaves a lot of free cash for other areas like a good sub, projector, etc.