Although I have commented on this in lots of other threads, I always like to go on about my favourite amp!
Tubes: All stock. The Mesa badged '6L6 GC' sound great. If it ain't broke, don't fix it!!
Cabs:
I personally love
1) the 27" 1 x 12 extension cab. 1 c90 and it sounds fantastic! Good for everything but best for clean and leads.
2) The 27" 2 x 12 extension cab. Great if you want more crunch, a bigger sound, and less bass.
3) For heavy arsenal, the Mesa Traditional 4 x 12 Rectocab sounds great. A nice round and mid focused tone. Less gainy and chunky than the 1 x 12 but it sounds HUGE!
I have heard that a 2 x 12 Horizontal Rectocab and the Standard 4 x 12 rectocab both sound great with this amp as well!!