Had a "standard" JL-2 that I bought used and it worked well with one re-tubing for 3 years. It handily outclassed anything before it, tube or SS. Then a bad tube took out a resistor and damaged one of the boards. After some attempts at repair myself, took a deep breath and sent it back to CAT. After some discussion and another very deep breath, had it upgraded to MK2 signature. Just got it back and the improvements are NOT subtle. Was already the best amp ever in my system, and is now substantially better. The newer boards have the offending resistors spaced out and sized more appropriately so bad tubes in theory do less damage. Haven't had it back long enough to comment on reliability, but the sound is very greatly improved, and the earlier version was nothing to sneeze at.
