POSTPONED ... Going to see if I can still use just the power amp section. If not, I'll release this back to the wild. (you all).
Yes, it will most likely work perfectly unless there are problems beyond what you've encountered. Any of the line level inputs should work, a preamp puts out the same 2v maximum that a CDP or DAC does, but with a volume control included. My two DACs both have volume controls and I can hook them directly into my power amps, which is basically what you have.