Tube changes did warm up the Powerball, but it didn't solve its solid-state like responsiveness which just made it flat-out not fun to play. I thought the Fireball absolutely CRUSHED the Powerball in both tone and response.
I'd love to try an ENGL Invader sometime, but I'm pretty content ampwise right now (plus I'm probably going to pick up a VHT Sig:X and Brunetti thru my store
)