Hi Huntermusic, your Esoteric K-01 has a very nice low 47ohm output impedance and your Krell has an equally very nice 100kohm input impedance. Perfect recipe for a passive preamp.
You should for peanuts ($49) try out this cheap one first and see what you think, then if you like what you hear and want some thing more esoteric, keep in touch.
http://schiit.com/products/sys
Cheers George