The only good thing about Pcsforeveryone.com that they have a larger selection of hardware that you don't normally find in a BestBuy's or CompUSA. Other than that, they're just as overpriced as any of the regular retailers such as BestBuy's next door or MicroCenter down the road in Cambridge.
I'd stick on line vendors, unless you can get a good deal on a rebated item at BestBuy's or CompUSA. MicroCenter is another place that overcharges like crazy also, but they've got the best selection of heatsinks, fans, and other minor parts for PC enthusiasts. Also, there a couple of small PC shops right next to the CompUSA in Woburn that's not bad for misc parts as well.