Budget Enthusiast

I posted earlier but forgot to include this question. My KG4's have some dirt/mud stuff on the grills and a bit on the divers and surrounds. Can i safely clean this with a damp cloth, or is this a bad idea on the surrounds. Also, is there any way to visually judge the condition of the surrounds if the rubber is not cracking at all? Mine have some grey discoloration but still seem quite solid. Thanks for the help and it's great so see such an active forum on such older speakers, it really makes me confident that I'm going to enjoy these!

I just picked a pair of KG4 (WO) for $100 and was hoping I could get a little advice. Unfortunately, I have little to no disposable income to spend on my audio appreciation. This means I am running these speakers off a Sony STR-DE597 low cost HT receiver, and can't afford a quality amp until I find one used for $50 or under. I am also in a small, concrete walled, college dorm at the moment. With that in mind, can anyone recommend optimal placement and/or receiver settings for these exciting new speakers? Also, does anyone know what these are realistically worth? I have no intentions of selling them but am curious. Thanks a lot, Paul