Hi Chris- Since I know you are at least contemplating a switch to a 300B based amp- Here is a link to a review of 11 different iterations/brands. You may find the observations/info helpful: (http://www.stereophile.com/features/229/index.html)
Amplifier for Avantgarde Duos
I'm looking for an amplifier for my Avantgarde Duos. I'm currently using an Art Audio Carissa with an ASL Flora for the pre. With this combination I still get a shrill presentation on some recordings. My pre has a nice rounded top end so I feel comfortable with it. Does anyone have any suggestions for the amp. Again I prefer something that softens the shrillness. Some amps have a lean top end. The Carissa is almost there.