I mean, I already have an AVR that supports wireless thru MusicCast in the Yamaha RXV681. Is the new Sony AVR better/different than what I currently have, that is worth the investment?
Without seeing any reliable reviews, I'd guess the new Sony's probably not worth spending on just for this purpose since you already have a Yamaha AVR w/ which you're otherwise very happy. I really doubt Sony's wireless speakers would be any better than Yamaha's (w/out some good reliable reviews to say otherwise) -- personally, I'd probably trust Yamaha's powered speakers for good fidelity sound more than Sony (leaving aside the wireless aspect for a moment)... plus I also feel like Yamaha receivers probably represent better values than Sony's based on past history... though maybe that's changed in recent years...
But sure, maybe wait for some good, reliable reviews (maybe at Audioholics.com for instance) on the new Sony AVRs first before committing... although you might end up waiting another 1/2 to full year for such reviews...
_Man_