cadence151
I would just stick with what you've got, especially the amp as these speakers need that kind of drive .
http://cdn.stereophile.com/images/archivesart/C72fig1.jpg
You could for a trial period try the Schiit Freya preamp it's a 3 in one balanced or single ended output, with a very good volume control, can be passive, active tube, or active solid state, with the Krells "Input Impedance 100 kohms, a great match with all three modes.
At $699 it's a steal and you can return it if not happy.
http://schiit.com/products/freya
Cheers George