First Watt F8

According to Mr Pass, the specs are actually improved for the F8.

It is similar to the J2 amplifier, but has only one front end transistor instead of six, operated as a current feedback amplifier (CFA) as opposed to the J2's voltage feedback (VFA) differential input. This front end is more consistent with the single-ended approach to amplifier design and yields a purer second harmonic character, less distortion with lower negative feedback, greater bandwidth and higher damping factor.
 
Might come down to whether you like simpler signal path or balanced operation. I wouldn't predict J2 fading in the limelight.

Wouldn't be surprised if he made F8 first, then somebody said, "Why don't you make a balanced version?".
 
Ive built a $#^/ ton of amplifiers and listen to a %$=/ ton more. I'm very aware they sound different and ound does do not always correlate with the specs.

FW amps are all fantastic when played through the appropriate speaker. Happy?