I'm not a fan of adaptors, I've heard some horror stories about tube rolling with them (not in Riviera but enough to keep me away).Planning to check out any e180cc/7072 (no adaptors) or ecc40 with adaptors?
From memory 70% of the gain of the 12at7 which will give you a bit more usable volume range
Will take a look at the other suggestion, this first round is based on recommendations from my tube expert