What do you guys think about the Polk RTiA9?
They are $500 on newegg.
Do you have any suggestions for something <$500?
I'm also looking at the Pioneer SC-1222-K($550), would that be powerful enough for the Polks?
Out of your list I'd go for that XV-15 for sure. You wanna feel the bass? That will do it for you. Congrats on the A9's.
Hsu makes a wireless sub (not exactly cheap but a good performer). Not sure about the other companies. You would normally set your X-over to 80Hz and anything below that goes to the sub and takes some stress off your receiver. For now just enjoy those nice speakers.