Another shop I visit monthly, Sonic Boom is definitely Toronto's music super store. They have a massive floor space selling all manner of new and used vinyl, CDs, DVDs, books, clothing and accessories.
Vinyl appears to be priced using a value scale, so it is pretty easy to determine ahead of time what you will be paying. While I have not found any outright mind-blowing rarities at Sonic Boom, I have found some nice obscurities at good prices. They are open late 364 days a year.
782 Bathurst Street, Toronto
416 532 0334