I build my own from components. Then I can have high end components in areas that are important to me (video card, for example) and slightly less than high end everywhere else. With corporate built machines, often you can only get the high end video (or whatever) with the top of the line CPU, etc. I don't like packages; I want to select my own components.

I buy everything from newegg, though I used to use mwave and was happy with them. Newegg has better service and comparable prices.

FWIW,
Jim