I had the JEL 20 and still have the red 1x12 cabs.
I hated the JEL 20. Disclaimer- I only played Strats thru it when I had it.
I found the Bass excessive. The Treble was ear fatiguing, IMO. I blamed it on the EL 84's.
The main issue was the excessive brightness. You had no way of turning off the bright cap (s) on the Gain channel. This has been addressed in the JEL 50, which has bright switches for BOTH channels.
I even blamed it on the 1x12's, but they kick ass with my Soldano X88ir.