OK, I am going to say something to this thread. I was trained by the USAF in electronics. When people start talking about watts vs loudness, I cringe. A 20 watt amp, no matter if it is tube or ss, will deliver 20 watts of POWER to the speaker. If you have an 8" speaker, it will not sound as loud as if you have a 15" speaker. It comes down to how much air you can move. Cabinet design can give you a bit more air movement (open back or closed back), but the amp is still delivering 20 watts. The sound pressure is what you "hear", the watts are just the power available to move the air.