I'm in the same boat. The foam surround on the speaker is shot. So, replace the speaker or just the foam surround?
It look like the speaker is 6 ohm, so I can't just drop in a 4 Ohm 6.5" from JLAudio (although I'd love to) I've found a few answer searching:
Foam surround replacement:
http://www.amazon.com/Klipsch-Speaker-Repair-Replacement-FSK-6-5/dp/B009DNMR8I
Mavin Replacement?
http://www.ebay.com/itm/NEW-Super-Sounding-6-5-Woofer-Mid-Range-Speaker-125-watts-RMS-6-ohms-PAIR-/360399201301