I hear the Onkyo HT484 is pretty good for the money. It does seem to be discontinued or something.
The Kenwood HTB-503 got some good reviews...
http://www.audioreview.com/reviews/A...ct_50649.shtml
Just make sure that your speakers aren't too close to your monitor, or else you will be degausing like a madman. The center channel should be magnetically shielded, though.
Kenwood also has the new HTB553 system too. Be sure to check that out.
http://www.800.com/prod.asp?p=4360