Plan 9 is a great resource for music in downtown Richmond. They offer new and used CDs, and if you buy a lot of music (like I do), you know the value of buying used CDs as often as you can! The quality of their used CDs and DVDs is very high, so you don't have to worry about scratches or cracks rendering the discs unplayable. I know they buy back CDs as well, but I don't know how much they take or what they pay since I've never tried to sell anything to them.
My only complaint is that the store is a bit cramped, but that's just old age talking =) Plan 9 has great ambiance and a wide variety of music for all tastes, from hip hop to oldies. If you're looking for an alternative to high dollar music stores, why not give them a try?