Best processor that is excellent for 2 Ch music

I'd recommend a used EAD Theatermaster 8000pro or 8800pro.

I'm using an Arcam AVR300 which is pretty darned nice with an after market power cord.

I also highly recommend Cary Audio HT separates - incredibly good sounding gear for music. It has the house sound of their high end 2 channel gear with the processing power for HT.

In fact, I like it as well or better than Lexicon, Meridian and other SOTA gear.

Cary turns up here used once in awhile, where is is usually snapped up by music lover types who want to integrate music & movies into one system.

I don't doubt the Cary is better sounding as a processor than the pieces Rackon mentioned, indeed. Still, none of these porcessors are going to be as good in the preamp department as a standalone quality higher end preamp! (especially tube pre's, used, for the money!). While the higher end AV pre/pro is going to have good dac's, and good overall processing, the other portions of the preamp stages, analog out's, buffering, etc, isn't going usually be the "ultimate" 2 channel pre, In my experiences.
Still, it's always all usually a compromise. Even high end rigs have lots of compromises, whether their owners think so or not. However, some of these better av pre's have gotten good enough that most would easily (including myself for the time being, as I'm concentrating on HT) satisfy both 2 channel (digitally dirrect mostly) and HT needs! There's some good pieces out there yes.

For your less than $1,500 target you can pick up a used Cal Audio 2500. Outstanding processor and very good pre-amp functionality. I liked it slightly better than the Classe SSP 75 which is another outstanding unit but not one which would fall into your price range. The downside to the Cal is that they are out of business so repair could be an issue, but the upside is that it will be tough to find better overall performance within the $1,500 budget.

Why has no one mentioned BRYSTON!! Though I don't use this, the sp1 and up uses basically the same pre as the two channel system.