Nah, the powertube section won't really affect how much gain you get, at least not a lot.....I have EL34's in my 800 though. When you referred to El-34's breaking up sooner, that's the effect they have on the speakers. They make the speakers break up sooner. If your not getting a lot of gain with the volume at 8, the powertubes aren't the problem...

I suggest swapping out the pre-amp tubes.