Sonic Boom is a huge used (and new also, I think) CD and vinyl store on Bloor just a few stores east of Bathurst, North side of the street. The staff is really nice. They don't offer great rates to buy your used cd's, but with cd sales these days, it's understandable. Once I sold a bunch of wrapped, new cd's of recent releases and felt kind of ripped off at the low offer, but it was my choice and I needed the money. Otherwise it's a great store and the basement space ware they have live shows is great.
The 'in-stores' are always free and have so far been completely fun so I'd recommend anyone going - especially if you don't know about the band and don't want to spend money to get a sample.