What i was hoping to achieve was more of a B15 type tone from one of the channels in the same way that some guitar amps have differently voiced preamp sections, being able to have one amp with 3 or 4 classic sounding preamps in would be ideal. What made me think of changing valves was the already present baxandall eq on 3 of the 4 channels, everything i'd read was said the 6SL7 valve sounded more musically pleasing and had been swapped using a secondry 9 pin to 8 pin converter. I'll the trying lower gain valves first tho.
I'm not looking for exact cloned tones as that'd be impossable to achieve in one valve amp without some form of modeling.