I'm currently using a SEP (single-ended parallel) 6l6 amp made by Niteshade. It puts out 14 watts of pure Class A power driving the Fortes to whatever level is necessary. I do listen to much complex music (just finished listening to Mahler's 9th) and small acoustic groups alike. I also alternate this amp with the TAD-60 push-pull amp which can be used in a SE fashion or ultralinear with 6l6 or other octal tubes. For this amp I get either 25 or 50 amps. But I also have used a 4.5 watt 421A tube based amp, which, I agree, is a mite too little for Mahler. Have fun!