As you know i haven't heard the polks.. That being said i agree with your opinion...Two different speakers but definitely neither are harsh. That said, I very much agree with you, especially when you factor in the price and free returns. My main point was that something like the 530s in the $300 (or so) range along with a sub would certainly be greater than a $600-700 pair of speakers with no sub.
At $600 a HSU VTF2-mk5 would be my choice. Actually I calculated it at $643, but its certainly one of the best subs for the price. Just note that it is quite large.