See if you can get the case locally, as that will make up the bulk of your shipping costs.
If you intend to get the OS from MSY (I assume the OEM version), you also need to buy the motherboard and CPU from them as well. Due to OEM licensing it can only be sold with a motherboard+CPU in tow.
I'v had good experiences with PC Case Gear, their customer support is awesome and the guys behind the pickup desk are pretty good.
MSY is more like your stereotypical computer shop, overflowing with components in a barely organized chaos, but they do offer the cheapest prices on what they do stock and have had no issues with them so far.