Technology for the long haul when purchasing specifically for an Apple Airplay? That doesn't make much sense. As if Apple is hot now, it may not be in 5 years or more. I would also like to say that Apple TV if you already have a receiver was a good choice. Airplay is a one to one connection, and I would tell you that Sonos Connect would be a better solution for a person thinking "ahead" Sonos is completely compatible with 3 popular platforms, and does everything you mentioned. However, rather than just playing your Apple music collection where the receiver is you can play it anywhere in the location if you choose to add on.
Marantz is not the "same" as a 3313, they definitely sound different for one. They do share a good bit of tech for sure, and it seems to be the common consensus to be crazy for Audyssey. I don't think any of the popular brand receivers sound bad, but I can certainly say developing a taste after owning X brand is reasonable. I'm not trying to be controversial I just do not find that to be true.
edit: As far as sound quality issues with airplay vs apple TV. If you purchased it off itunes it was already down-sampled to 320 anyway.
FLAC and such are can actually be played on Sonos.
AVR: Marantz 7008 Phono: Pro-Ject Debut III Speakers: BW CMC2 + 2xCM9 + Energy 2xCB-10 (rear)
TV: Panasonic 65ZT60, Samsung 60F5300