I have two Fist Watt amps in two different systems. ( I’m a big fan) I run a J2 in my main system,and an F5 in a secondary system. I have four speakers that I rotate between both rooms. They are all around 8ohm speakers,however sensitivity ranges from 84db to 93db. I don’t listen at ear bleed levels. Both systems are using Aric Audio preamps that implement adjustable gain. (I love this feature)
Both of these amps do everything I need. For me, there are no short comings,and both amps do everything I need them to do. Obviously,YMMV.
Best of luck,
Ray