I have the Spendors (think they are great). I have not tried with 2A3, but have used 300B SE. It was sufficient about 95% of the time in my medium sized room, backing off the gain and listening a little quieter than I would have liked (I listen normally at moderate levels) made the amp usable with the rest. You are talking about 3 watts to the 300B's 10 watts, so my suspicion is that you are probably right on the cusp. This is a situation where I would try and borrow the amp you are considering or a similar amp to find out for yourself if you can live with it. Since SE amps are such a specialized item, I would try to find a dealer who would let you borrow one for a few days (give your dealer a break, he needs his "demo", offer to borrow it on Sat at closing time and return Monday and take GOOD CARE of it!). The other alternative; I believe Wright Sound (who makes some highly regarded amps) offers a trial period and makes a 2A3 amp, check his website for details (I have no connection to them...).