I've got the same amp. I find any pedal that I can adjust the level on will give more distortion on the 'leads distortion channel. I usually throw a compressor in front and rail the level. not my favorite distortion but it is gainier. I have a couple pedals, a modified boss, various others, right now my favorite is one from brian wampler. if you like the amps distortion and want more, increase your input level. otherwise you are searching for the Holy Grail.