(a friend)... straight out told me that based on his experience with a myriad of AN equipment, if I’m getting an AN power-amp then I should pair it with an AN pre or just get an AN integrated and that AN equipment doesn’t mix well with other brands
Hi @wenhaw, your friend was probably referring to AN amps' low input impedance which makes them unusual & difficult loads. It's not the end of the world, and the matter can be addressed by the pre's designer. You look like you already have an excellent pre (Cabernet?) so before you ditch it why not just contact its designer -- if you settle for AN, that is.
The Yamamoto is very good but I don't know if it, or any mid-range AN amp, can outperform your SIT-2.