JBL is solid, and the new Klipschs do not look bad, but I think these speakers are too much of a lateral move compared to your Polks, and not as much of an upward move as to be worth it. At the very least I would be considering some
Fluance Signature towers or some
RBH R55Ti towers. The RBH has a decent looking center channel companion in the
R56Ci. If you have a good subwoofer or two, also consider the
Hsu CCB-8 or
Ascend CMT-340. If you don't have a decent subwoofer, get
one of these or something better.