May I ask what your goals are for switching to a different amp?
I have the SDV 3100 HV in system one paired with the new Moon North 761 and find it to be a very good pairing (and it fits in my cabinet).
I have the SD 3100 HV (no preamp version) in system two feeding the Atmasphere MP 1 tube preamp going into Atmasphere Class D mono blocks. Also a good combination - which shouldn’t be too surprising because the North amp and Class D amps have very similar tonal characteristics and resolution.
I tried a couple of more expensive amplifiers but didn’t really find they brought anything more to the table. To be fair, I didn’t try anything that might be considered in the same class as the T+A units but I also didn’t feel like I needed to spend at that level to get where I wanted to go. The T+A units are that good alone.
I’d certainly suggest an audition of the Moon North amps if you have a dealer who carries them. They’re quite good. I can also comfortably suggest the T+A A3000 as a good and muscular pairing, but I wasn’t able to compare it directly to the Moon. My suspicion (untested) is it’s likely to be a bit warmer than the Moon.
Best,