Best Buy has a DJ section in most of their stores now, and they usually have the latest gear from Denon and Pioneer, but that's about it. They may have a Hercules or Numark controller or deck if you are lucky.
The best place to go would be Guitar Center. They usually have a nice selection of DJ equipment, new and used.
A suggestion would be to look up musical instrument resellers in your area. I have a couple around here, and they usually sell new equipment too, and the used stuff is 9/10 times just fine. I bought my second Technic 1200MKII used and it was fine for 10 years

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It's probably still playing fine, wherever it is! lol
----edit----
Best Buy has -TWO- DJ sections. One is usually by their mobile phones, where they have cheaper controllers and turntables/cd players. The one I am talking about is in the back in their PRO AUDIO section, where they have drum sets, keyboards, MIDI devices, etc.