Wow!!! Just got a quad of these for 40 bucks 8) (from someone who didnt like them in their Blackstar?) Anyway, I've put them in as a full quad and then paired them up with Groove Tube KT88's on the outside- these are definitely the best EL34's out there! Very balanced, 3D sounding and excellent mids- Also, I've noticed better note definition, especially with Marshall type modules... Looks like the price of these is ridiculous though- (Running up to 150 bucks a quad?) but if you get the chance to run these in your RM100, do it!