Besides the Relapse store (in case you don't know where it is, if you're on the busy part of South Street, look for a place called Jims Steaks, or something like that, and it's on that block and side of the street), there's a place on South Street called Rock and Roll Plus that used to be the Nuclear Blast outlet. They're still a metal shop. They're right across the street from Tower Records. Also along South Street, about a block or 2 from R&R+, you'll find some sandwich shop on the corner that's always playing really loud annoying music outside (like Motown and disco). If you turn down the street where that's at there's a place called Digital Ferret, which is more of an EBM/Goth/Industrial shop, but they usually have newer metal releases than the other stores.
Other than those, I can't remember.
Sorry for the crap directions, I cannot remember street names too well. Just park near the busy section of South Street, wander around and you'll eventually find everything. Ripperheads is in that area as well.