Prior advice suggested I go with a seperates for our home theater. Budget contstraints make it tough to go with good seperates versus a new receiver.

I have an Onkyo TX SR600 thats a couple years old but does get dolby digital ex pro logic II, extended dts es surround, cinema filter. I was planning on spending $2000 to buy a better receiver. Would I be better off buying an amp to go with this receiver or buy a new receiver. Suggestions? I've been directed to Yamaha Receivers and have read enough that I would probably go that route if I just buy a new receiver. Amps? If this is a better route which ones?

Marianne