In my opinion Bottlehead is conservative with the specs. I have 2A3 amps and 94DBW speakers in a room that is 14'X23'X8' (IIRC). My system plays louder than I can stand.
There are several things that go into whether you will be satisfied with the power of an amplifier. First is speaker sensitivity. Second is room size, the more air you must excite the more power you need. Third is your listening preferences. What volume do you listen to? According to my RS SPL meter I listen in the mid 80dB range. The system goes 10dB louder without a problem. Then what do you listen to? A symphony is harder to play loudly than Rock music, which is harder to produce than Bluegrass.
My classic, often suggested, answer is to find a Bottlehead in your area who can bring his amp over. Listening in your room, to your music, at your preferred volume is the best way to answer your question.
No question the Abbys and the 300B would be great unless you have a huge, HUGE room. They are a great speaker, I have heard them often.
