Decided to complete a full rebuild on this amp since I think I'm gonna keep it a while, I've had it for a few months and unlike any other amps, I don't feel like I'm missing something. I've already gone thru the amp and replaced all the transistors but I've hit a crossroads with these two fet's in the pre-amp. I can't seem to find a replacemetnt for them but I'd like to replace them for the sake of reliability. Anyone got any suggestions on whether it's worth replacing them and if so, what would be a good substitute? Also, just morbid curiosity... Any reason Pioneer chose to use mosfets in this section of the amp instead of a regular bipolar?