Yeah, my buddy just bought a 5150 iii EL34 50-watt head and 2x12 cab to go along with his 6L6 combo. He says the blue channel on the EL34 amp really scratches that Marshall itch he'd been having, and I don't doubt it. The thing I find kind of funny when looking through this thread is how so much of the iconic "Marshall tone" is the result of a relatively low gain preamp running through a cranked EL34 power section, yet every single JCM800 variant in that list is using a 6550 or KT88, neither of which is known for ease of overdriving, with a boosted preamp. So the master volume winds up pretty much acting as a "dam" to allow the overdriving of a low-gain preamp via external booster pedals, and the power section is there to be loud and clean. That's basically the conceptual recipe for a high gain amp, just using pedals instead of built-in gain stages to saturate the signal.
Whatever happened to Sancho?