Michael,
I had the Sapphire IIe/Sub 1 combo for several years. If you're asking will a 25w amp drive the Sapphs, no question that it will. I used a 12w tube amp to drive both the Sapphires and the subs. It wasn't terrific bass, but I found it very listenable.
If instead you are asking if this speaker system sounds good with tubes, the answer is YES YES YES. IMHO ACI speakers are made for tubes. You really hear the natural quality of the speakers with this type of amplification.
Karl