Nelson,
I think that's close to a perfect match. I have a P-306 and I'm impressed with its performance. The tone controls, if you're the type who needs these, have wider range compared with other preamps. Even the phono section is quite good. The P-306R should come out better.
Tony,
No, I did not get the defective M508. But wait, I just smoked my AU-X11 last night since I was experimenting with its external connectors -- 2 external preamps, 2 external power amps could be connected to it -- and in my excitement I plugged it in a 220-watt hole. It's been with me without problem for about 5 years now and has been an anchor in one of my major systems. If my technician can't fix it, you can take it away next year -- but beware, it shows 32 kgs. on my bathroom scale.