J2 I haven't heard but I have heard most of the other FirstWatt models (and the S-30 which I also really love). Of the FirstWatts my faves were the F2J and F3. I'd recommend getting on the phone with a FirstWatt dealer. Both Mark at Reno HiFi and Jon Ver Halen at Lowther USA in Chicago are great to talk to and can give a lot of guidance. Reno HiFi has an excellent return policy as well.
Whether the extra watts alone will be an improvement will depend on your speaker. How sensitive are they? What kind of volume do you listen at? In what size room?
Whether the extra watts alone will be an improvement will depend on your speaker. How sensitive are they? What kind of volume do you listen at? In what size room?