Hi Dennis,
Congrats on your recent acquisition of the Criterion. I have not had the opportunity to hear the Criterion but having heard the Corus, I can understand where you are coming from. JDRG actually rates the Criterion above the Corus. Having a high quality preamp most certainly puts to rest any previous concern whether to go direct to power amp or not. The K-03 is surely singing now as it should. With the preamp in the chain, every other component in the system gets upgraded simultaneously and of course, the whole is a whole lot better than the sum of its parts.
Cheers! J.