I did cut and glue some rubber I found to replace the surround:

Amazon.com: TORRAMI Neoprene Rubber Sheet Roll 1/16 (.062) Inch Thick x 12 Inch Wide x 48 Inch Long for DIY Gaskets, Pads, Seals, Crafts, Flooring,Cushioning of Anti-Vibration, Anti-Slip : Industrial & Scientific

It got rid of the crackle but the speakers sound a little muted now since there is not much flex. I ended up just bypassing the sound altogether and only using tower speakers however.