.Well, the Krell KAV-250p has a "home theater passthrough" mode that can be configured on input #3. You would just take the left/right pre-outs from the Yamaha and connect them directly into input 3 on the Krell. This will save you the cost of the RCA switcher and extra RCA cable. Also, I think you'd get a bit better performance from this 2-channel preamp then you would from the multi-channel Pre/Pros you listed.
http://krellonline.com/assets/support/KAV250P_V000_MAN.pdf
Referenced on page 8 of the user manual.
Auxinput, thanks for the input.
The Krell 250P interests me, but time and time again, I'm reading that the Krell sound is more forward and brighter than Classe, which is what I'm trying to avoid. I guess I can always try various pieces and sell what doesn't work for me.