Thanks all and yes, upgrades sure are fun!
Got a little more sitck time in with the new unit, mainly dealing with music. I also did the latest firmware update, which was painless via usb, but haven't noticed any differences and no pause on music playback was added.
I can say for sure that the 8063 has much better (and louder) audio output than the old one. The 5750 must have been struggling at higher levels as I could never really exceed ~95 db SPL without the noticing the sound quality degrading, mostly with music, less so with HT. On my tests today, with music I've listened to countless times, I was in the 104 db range and it was still sounding clean, nice! Of course these SPLs are beyond my comfort level for extended listening but sometimes (and for some songs) you just have to crank it up.

I do appreciate the build/sound quality on RC70s more now, I honestly didn't think the difference would be so apparent.
During the holidays I'll spend some time with REW and maybe adjust the PEQ settings a little manually. Not that the YPAO didn't do a good job, I think it did but there is usually room for improvement. I also think I'll add in a few more sub settings with a little lower output and cut the lower frequencies off a bit for music.
Steve