If the amps in the 1500 are the same as those in the 1400 (which were tested at a meager 35 wpc w/ all channels driven by Sound and Vision) then I would expect the Signature 2.1 to be a solid step up from the 1500's internal amps. The 1500 should, however, be a great processor and while the internal amps may not be the strongest they have/are serving many well.
Whoa, 35wpc! I do know that they improved the amp in 1500 (went from 110x7 to 120x7), but I guess based on the S&V test I shouldn't expect more than 50wpc or so.
And yes I do plan on using the 1500 as the pre/pro.