I am (or was) mostly a bass player, and to be honest, I doubt you'll have much trouble keeping up.
From experience, I'd say the difference between valve and SS isn't like what we experience here on guitars, because on bass we're not distorting our amps (usually) and on bass the frequencies are far lower and need more power?
I'd be more frightened if he got a decent 8x10 with very very efficient speakers, and that's where the guy with the mark bass is probably going wrong... one thing I've noticed with bass players is, most of them wouldn't go inside their cab and think about changing those speakers inside, completely different breed. Even changing pick-up's seem a little alien!
And hey, don't you have EVH's signature on your amp somewhere? I'd say that's bragging rights, right there.
Adam Clayton uses Ashdown gear, a 500+500 stereo power amp, solid state... with a hybrid pre-amp, and a sub-harmonic generator... which is just immense.
