I know the denon 3805, 3806, and 4306 has all that stuff. I'm not sure what you mean by THX surround sound. Pro Logic IIx, DTS-ES, and such is what I think you mean. If that is in fact what you mean then they both have it. Check them out though. Crutchfield is a great place to "shop" (lots of pictures and stuff) but not to buy, unless you want to pay more than anywhere else, although they do have great customer service.

3805 - http://www.crutchfield.com/S-ttjtDTNjuOR/cgi-bin/ProdView.asp?g=10420&I=033AV3805B
3806 - http://www.crutchfield.com/S-ttjtDTNjuOR/cgi-bin/ProdView.asp?g=10420&I=033AV3806B
4306 - http://www.crutchfield.com/S-ttjtDTNjuOR/cgi-bin/ProdView.asp?g=10420&I=033AV4306B


Denon 5803 Denon 3910 Axiom M80ti's, QS8's VP150, EP500's (7.2)