Now that antiseptic virgins have started selling overpriced CDs at the corner of Newbury Street and Mass. Ave., it's nice to know the bad girl still lives next door. The Back Bay Newbury Comics store looks like a pop-culture flea market, with everything from DVDs to T-shirts to X-Men action figures. But, ultimately, music is all that matters. If a rock anthem, hip-hop rhyme, or sugary pop song has been pressed into vinyl or onto a CD, no matter how obscure (or bad), odds are Newbury Comics has it. And the kids behind the counter might look like human graffiti thanks to their tattoos, but most are walking music encyclopedias who are usually glad to help out.