Definitely stay with tubes if a Krell 350 watt amp can't do low end it's on the amp not your preamp. Are there better tube preamps than the AI? Sure do you have a budget in mind?
Tube vs Solid state for Preamp
Like opinions on this match up
Running audible illusions L3 preamp. into (jumpers removerd) Krell 350 mcx in a Biamped arrangement.
Would going solid state be an upgrade in Lowend control of the krell