On those speakers they'll do more than the Krell. They won't be as highly resolving as you're used to. That is what Krell does well. Soundstage should be just as good if not better.
Tubes last a while but if you leave the amp on all the time they'll wear out. You'll probably want an amp that is self biasing which means balance the voltage at the tubes and some track use time. Every once in a while a tube will go out so you might want a good tube tester and a few extras around. I would guess every other year you'll need to change them all out which is nothing more than screwing out the old ones and screwing in the new ones. Yes they require more work than SS but it's not a lot.
Tubes last a while but if you leave the amp on all the time they'll wear out. You'll probably want an amp that is self biasing which means balance the voltage at the tubes and some track use time. Every once in a while a tube will go out so you might want a good tube tester and a few extras around. I would guess every other year you'll need to change them all out which is nothing more than screwing out the old ones and screwing in the new ones. Yes they require more work than SS but it's not a lot.