For the Stratos, the dual mono (180 wpc) is one way to go; 20% more power than the regular Stratos, if the specs are to be believed. One just sold here for $1250. I have the extreme version, and enjoy it; I'll also join the choir about how great Klaus is to deal with, including supporting gear purchased used. Don't know the Krell, but it looks like a bigger investment for you (one listed for $1850), since you've got the pre covered.
John
John