I was wiping down my speakers with a microfiber cloth today and noticed what appears to be some residue on the top of my EP600's surround. I dampened a corner of my MF cloth and wiped a bit, but that didn't seem to help. I searched here for awhile and on Google but couldn't come up with anything. Does anyone have recommendations?

A: Epic 80 * 600 / Integra DTC-9.8 / A1400-8
V: Samsung HL-S6187W / Tosh HD-XA2 / PS3 / Oppo 970HD