bigwill made a post about this recently - it won't make any discernable difference in sound, yet the extra power will be nice for when you really want to crank it. He added an Onkyo amp to his denon 2803, and was able to get it a bit louder(when playing five channels, not two - only the most horrible receivers are power shy when it comes to two channel music). Receiver amps work nicer powering three channels than they do powering five. Only the worst receivers, when barely pumping out anything under 80 Hz, sound bad without an external amp.
If it were me, well.. you already have an amp - I'd get another STF-2.
It'd make a hell of a difference, and it'd be $300-$600 less than the amps you're considering getting. I thought you didn't have an amp yet.
