@leahy ,
This is going to be an interesting direct comparison you plan to do.
1 Active tube preamplifier paired with a 300b SET circuit (Class A) DHT output tubes vs
2 Integrated amplifier with a passive preamplifier section, push-pull (Class A/B) circuit using pentode el34 output tubes. I have no doubt that you will hear distinct differences between these two. This will be fun and informative.
Charles