how much power dissipation are you able to get out of a single IRF240? It would be a trade off I guess. It seems that the design is already bandwidth challenged, or at least requires a lot of preamp muscle. I was think of making a cascoded/current sourced (I'll let Jam and Grey fight that one out) balanced line stage to drive it with, probably integrating it into one chassis/channel- more of an input stage than a preamp really(don't know if I already stated that). I would like to keep it to two stages for the sake of simplicity. My problem is that the heatsinks I have are not that great- 2.2c/w. I will be using them in groups, hoping to get this thing cool enough to push enough bias through for 20 watts. So, where do I compromise- More devices in the output with a driver, or less devices w/no driver and less power? My speakers are about 92.5db- 1w, but I do like to turn it up a little. I eventually will move these to just tweeter duty.
Steve