Try the Bryston 7b-st/14b-st before you give up on Bryston, they are a lot bigger than the 4b-st with gobs of grunt. Krell is a good choice as a sub amp as well (provided that's all you're planning to use it for...), though kinda pricey for "just" a sub amp. And as you've already figured out, you're gonna need a lot bigger Krell than a KST100 to get there from here. In the end, you may go through a lot of amps and samoleons and still not do any better than that Crown. If it were me, I'd keep it and spend the dough elsewhere.
what is the best sub amp.
i have used a krell kst 100 strapped mono for years running a jbl pro 4719 sub with two 18s in it. i have been very happy with this amp until i watched pearl harbor. the kst started to loose it's control over the sub. i found a crown macro reference and put it on the sub. the crown killed the little krell, and never lost control at all. my main question is would i be better of with this crown or getting a larger krell? thanks alot for everyones thoughts.