The factory grilles stay. The foam baffles stay (if they're not completely demolished). The thin dust cover on the inside of the grilles is probably rotten out, so rip it off and replace it, if you want to. Don't just go with a brand name. Choose good speakers that fit your needs. I recommend Infinity Reference 3-ways. They are a bit on the expensive side ($120), but they sound fantastic. Also base your decision on whether you connect the speakers to an external amp, or to the head unit's built-in amp. I heard a lot of good feedback about Boston Accoustics for system without an external amp. I never heard of anyone who liked Sony Xplod speakers. If you're buying on Ebay, make sure you're getting a warranty.