I've tried many distortions in my guitarist life, but I've never found one that totally pleased me. Starting out with a Peavey TransTube 112, I first used amp distortion, then used the BOSS Blues Driver for a while (yes, it can do heavy!), later replaced by a BOSS Metal Zone. Then I had the Behringer V-Amp. Never could get a good sound in combination with an amp out of that box. I also tried the BOSS GT-8 and the PODxt Live. These multis are awesome pieces of equipment, but they never worked for me in combination with an amp as far as the distortions are concerned. Finally, I got my all-tube amp: a Peavey 6505. This monster doesn't need any digital distortion, of course. Recently, though, I've been using an EHX Little Big Muff to get variety in tone (and it works well). Other distortion pedals come out with too little juice, in my opinion. The 6505 head is extremely bright. I also got an EHX Nano Metal Muff, just because it looks cute. And well, it sounds good, too! For little gigs, when I don't want to carry my amp around, I also have a Line6 ÜberMetal, which I can run through any amp and get a decent heavy sound (and it has a built-in noise gate). So, but really, I am all sold on my Peavey's tube distortion and will continue to use it.