Despite the sweetness of the Costco deal, in the long run you'll do better dealing directly with Dell. I do not believe you'll be able to use My Tech Team with a system purchased through Costco. If you keep an eye out on the deal sites, like Techbargains and Slickdeals, I'm fairly confident you can get a deal equal to that of Costco at Dell.
Costco has some pretty sweet deals on Studio XPSs right now, but wondered about adding a couple things after purchase. One is the 9000 comes with a NVIDIA GT220. How expensive is it for me to swap out to a 240, and does that void the warranty. And, can My Tech Team be added? I only know of XP and thought I might need a little "hand holding" to get up to speed on 7. What is XPS support like? I hear horror stories about Inspiron support, but have nothing but good experience with my Pro Support on my business laptop.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic