im gonna have to school you people. first of all, the difference between a dual and triple rectifier is so insignificant that saying you can tell the difference is retarded. a rectifier is a means of how power is sent throught the amp. there is 2 ways, a tube rectifier (which is spongy and makes it so your power isnt always available, so for like blues and stuff) and then there is silicon diode (which is what marshall, and pretty much everything else has, which is a diode, making power always available, and for anyone playing metal on this site would probably use, unless your brain dead). so now that we know this, the difference between the dual or triple is $150 , for what? for 50 watts no human will ever need (besides discordance axis, because he played 900 watt power amps, which made him deaf and broke up his band) and an extra set of tube rectifiers. the 5150 is an ok amp at best. messy distortion, and built like shit. actually they are made by crate if you must know. and crate is shit(the other guitar player in my band has a blue voodoo, and that amp is subpar). so... marshall are good. thats it. they are made by korg now and have left quality control guidelines. mesa are still made by hand, but if you can find an old 2 channel dual rectifier, that was the shit. the difference here, is that the new 3 channels share the tone between the 3 channels instead of 2, which was the ballsiest sound. thats why when you see a mesa in preamps, such as the line 6 pods, it says like, 94-96. thats what you want. you see them on ebay alot. they are awesome. i know all this because i worked for guitar center fo a year or so, and i got all the real training on the shit. if you have any other questions, ask. thanks