Just got my AV-710 in the mail and I friggin LOVE this puppy
I've got the A2 line-outs running into the line outs of my z-680s for 5.1 gaming, then the optical out to the z-680s for speaker listening and (for now) my HD497s into the aux out for head-fi goodness. I like this setup, since I don't get windows noises or any of that crap through my phones when I am listening.
All I can say is I am gonna cream my pants when I finally finish my PPA and get some SR225s
One thing I noticed, though, is that when I plugged the optical out into my z680s the bass went through the roof! I mean like 12 dB of boost! I've managed to tame the z680s with my A2 by bringing the sub level to ALMOST zero but even at that setting the bass is really thumpy with the new optical out. Though I will say it is much tighter over my old A2 analog out, so I almost don't mind it. I don't get this effect with the analog out on the AV-710, but I have no idea how my speakers could be making that kind of boost.
Oh well, either way I am a very satisfied head-fi'er