In bongripper, the tuning absolutely had something to do with it, never could get tube amps to react the way I wanted them to, they never could get my low, low end out without sounding really muddy and unclear.
But for cstvt we play in D (sometimes F, but F a half step above E standard), that was all just competing with a heavy handed drummer and guitarists running 200 watt rigs on both sides of me.
I'm not trying to start **** or whatever, tube amps are sweet. I wish I could find one that would work for me, I've been thinking of picking up something that's more light weight and less costly to maintain than an SVT to run in combination with one of my hybrid amps. I had ran a rig like that briefly when I had my Sunn and SVT-II and it was the perfect mix of that undefiniable tube amp sound, plus the clean bottom end and headroom from my sunn. I ended up not using it live since it was carrying around a 80lb amp to not really increase my volume at all, but rather just get a slightly different tone. Now a 40lb amp...that would be something to consider.