The Sony will work fine, but it lacks a bit, particularly compared to Yamaha/Denon/Marantz, and that's auto setup/room correction (YPAO in Yamaha, Audyssey in Denon/Marantz, Sony's DCAC isn't as well regarded) as well as network connectivity (it does have NFC and bluetooth builtin but not wifi). I'd look at the Denon X1100 and Yamaha V579 at accessories4less for example for $300. Those are refurbs with lesser warranty and no store to return it to if something goes awry on the other hand, so there are tradeoffs.
Your budget is a bit slim for the better subs but think I'd rather have
two Sub-1200's rather than the Polk or ML subs for $300.