Dear @milt808 : " a warmer sound with more harmonics. "
First the harmonics are developed by the recording source we are listening it and those harmonics have changes through all the signal path where that signal must travels in our room/system till goes in our ears/brain/body. A good room treatment and fine tunning the subwoofers SPLs can help for that warmer sound you are looking for that again depends on the signal source. The issue is not about tube amplifier because your speakers impedance at a critical 20khz frequency is down to 0.43 ohms and I don't know yet a tube amp that can handled with applomb that speaker impedance.
In my opinion this is the amp for your system and I think you can't go wrong with:
https://parasound.com/jc1+.php
Regards and enjoy the MUSIC NOT DISTORTIONS,
R.