Oh you've now got tha br00talz!! ha ha
You'll find tips around the place for tubes to use.
Quite a few people have these 'bias modded' to allow the bias to be turned up a bit. Be conservative though if you get this done and use a bit of that extra range but don't wind it all the way as you could end up chewing through tubes like there's no tomorrow.
Standard tricks people use with these:
Tubescreamer with level dimed and gain on zero (I find this helps a lot)
ISP Decimator (you already have this!)
MXR 10-band EQ in the loop before the Decimator
A lot of people like an MXR Carbon Copy for a delay in the loop (last thing before the return).
This would be GUITAR -> SCREAMER -> AMP (THEN IN LOOP YOU HAVE EQ -> ISP -> DELAY)
Of course you can add other things if pedals are fun for you but my advice is avoid distortion pedals, they are really useless with these amps. If you want an extra boost on top of the screamer add a boost pedal in front on the screamer.
The only problem you are going to have with this amp is cleans. I have never heard of anyone getting a good clean out of one so don't bother. Hopefully your Mesa can do that for you
