The VSX-822-K will be fine to power your Polks, and it has a subwoofer output that will work with your Def Tech sub. Are there any specific features you're looking for? Do you think you'll add or upgrade speakers in the future? All things to consider, besides just amp power. The VSX-822-K has room correction, 3D capability, and network streaming, all handy features at this price point.
If you're willing to purchase online, take a look at this Onkyo, very near the price of the Pioneer you're looking at. It is 7.1 channel, 4K ready, and has Audyssey room correction, which I believe to be better than Pioneer's MCACC. Just a thought.
http://www.accessories4less.com/mak...7.2-Channel-Network-A/V-Receiver/1.html#!more
The Pioneer is not a bad deal at $208 if you like it, but I'd personally spend a few more bucks on something like the Onkyo.