Whats the krell sound?

Bright.
Very bright.
Did I mention bright?

Krell sounds liquid and smooth as well to my ears.
True not as warm as some tubes, but the sound is good enough so that you won't miss the warmth - it is pleasant enough on it's own terms.

I also like the dynamic quality of Krell - it breaths life into music in a punchy and satisfying way that most tubes cannot.

I don't think it's correct calling Krell Bright! I've heard Krell sound bright in certain system combinations. But that goes with lots of gear combo's. The more analytical you get, the more things can tip "hot" tonally. It's a balancing act indeed.
As a line the Krell isn't bright though. I'd say it's good hifi effort, and better than most.

Ruthless. Too ruthless for most.

My opinion like 913nut is edgy very harsh and edgy at the top. Not a natural sound at all.