If you want to feel the music, your best bet is to spend your money on a powered sub. I don't see one listed.
If it were my $600, this is what I would do.
http://www.svsound.com/products-sub-box-pb12nsd.cfm
Granted, your system needs some improvement. But, this will add more to your system than any other item at the moment.
Upgrades will always be in the future. But, you will not need to upgrade your sub for a very, very, long time.