Why not just put all that money toward a kick a** sub? Those JBLs would be a sideways move, you would need Studio Ls for an upgrade.
http://www.edesignaudio.com/
http://www.hsuresearch.com/
http://www.svsound.com/products-sub.cfm
http://www.edesignaudio.com/
http://www.hsuresearch.com/
http://www.svsound.com/products-sub.cfm