I have a pair of Monitor 60 series ii speakers and a Harman Kardon HK 3480 powering them. I listen to mostly rock/metal although my GF likes to listen to rap and this setup is going to be used for parties. I was wondering what subwoofer would be a good match with these speakers. I saw the PSW10 but it seems like it wouldn't really be powerful enough. The PSW505 seems like a better option. Any suggestions?