You'll need to hear for yourself, only you can decide if they sound good when you hear them together.
As to the two speakers question, I'd been looking at the 609 a few months ago before I heard about the TX-8050 and the reviews were generally positive. The other thing is that this is one of the cheapest ways that you can go about bi-amping your speakers, so you can use four of the Onkyo's amps to drive the V4s.
The 609 also gives you Spotify functionality, and because it's networked, much like the 8050, then you get firmware updates, new product or new functionality and a whole bunch of stuff an integrated won't come near touching.