I'm seriously conflicted on buying the 4310. As much as I'm enticed by the idea of connecting with HDMI, I'm not convinced that it's going to sound any better than my Pioneer.
I can understand. I was moving from the Rotel, which had no room correction/E.Q. of any kind, and I had one HDMI connection wired through my ceiling to my projector with 4 HDMI devices, so I really needed the switching capability, and the Monoprice switch just wasn't cutting it. It was an easier decision for me for sure.
You, on the other hand, have a newer AVR with room correction, but the Audyssey MultiEQ XT is sure to be superior (whether or not you notice it is a different story), plus, all your gear is right by your TV so you aren't in desperate need of HDMI switching. Really, with the 4310 upgrade, you would be getting the upgraded room EQ, HDMI - and thus lossless audio, OSD, networking capabilities, better DACs and ADCs (could help it sound better along with Audyssey), and a new toy - since you have separate amps, the extra power matters not either...
Don't know what to tell you. I support you either way. Once you pull the trigger though, all of this stress and wondering will vanish, and you will just be excited for the new toy. Until then, I predict you will be waffling like a waffle.