I would try first the online shops of: Newegg, Zipzoomfly, Mwave, Ewiz, MicroCenter, BestBuy, Circuit City, CompUSA, Directron, even Page Computer and look for the best deal.
Funny thing: Newegg has a "sister" company, Chief Value. The prices and merchandise are almost identical, but every once in a while, there may be a thing or two cheaper in one over the other.
There is another online site, LogicalPlus.com. But with this one, I'd just be a bit more careful.