Killer doom pedal, I ran it into my '86 Mesa Boogie .50 Caliber with a Telecaster and an SG and a '68 Ampeg B25b with a G&L L-2000 and an Epiphone Thunderbird and sounds monsterous in all applications! With the SG into the Mesa, it really nails that Matt Pike/Sleep Holy Mountain tone - tons of bite, hairy top end, beautiful, creamy mids. Single coils sound very nice at lower gain settings and pushed by an overdrive in front to fatten it up. I wouldn't say it "stacks like tetris" exactly... ODs before the pedal sound very nice but not very articulate when you place them after the Holy Mountain. On bass it's a little harder to dial in a usable setting for me. You have to turn the Base knob all the way up to get enough low end for bass.The G&L's hot pickups drive it hard. It sounds nice really good with the T-Bird's lower output pickups and the Guide knob on a lower gain setting. Overall, it's a sweet pedal, great quality feel, not noisy at all (almost sounds gated in fact). It's a pricey pedal but if you're trying to nail that matamp/sunn tone without having to buy a $2k+ amp, i'd say the Holy Mountain is your best bet.