Ampli 7.1 or stereo?

I have a Nad T575 amplifier that I paid 1300$. I'm wondering if I sold it for about 900$/800$ and bought a stereo amp for 800$/900$, would I have a better quality? I do not use the 7.1, I listen to music, that's it!
I have used quite a few different stereo amps and multi channel receivers over many years in this hobby and have owned one NAD receiver which I thought was quite good. I currently have a powerful 7.1 channel receiver which I use for movies and T.V. That I have used for stereo listening on occasion.

I don't think I'm sufficiently qualified to advise you so I can only tell you how I came to my decisions regarding this question. The short answer is that you can probably improve your stereo listening using a decent stereo amp. That's not to say, though, that any stereo amp is going to be better than any multi channel receiver but in the price range you reference, one should be able to find some very decent used stereo amplifiers.

I won't go through a listing of amplifiers that I've used but I've been careful to audition and research them to the extent that I was never really unhappy with any of my choices. My present stereo amplifier is a Rogue Audio Sphinx which I bought new for only $1300 and it may be the best sounding amp I've ever owned; it would probably fit right into your price range if a used one could be found.

The bottom line is that, even though I don't consider myself to have the best trained ear, I can hear a quality difference between music from the receiver and the Sphinx, with signals from both routed through tube DAC's.
NAD does mfr pretty musical AVR's but most likely, a good 2-channel integrated will sound better. I think there is a used NAD C375BEE for sale here on Audiogon that is within your budget.