I'm not sure what "support from the Apple Store" has to do with it. Apple Store (and AppleCare via the telephone) will provide support for that iMac, regardless of where you bought it.
The thing to look at with the refurbs is that they're often build-to-order configurations that you can't get when buying in-store - maybe the "same price" isn't really the same Mac they have at Best Buy, though maybe it is (look really closely at the specs). I've never been overwhelmed by the depth of the discount offered with a refurb, but since it comes with an as-new warranty and cosmetic flaws are rare, any discount is better than none.