Welcome to the 'Mech Sue...Many of us here will agree that if you absolutely positively without a doubt have to buy prebuilt, Dell is the better system. The main reason many of us choose to build our own is we build according to what are needs are now. In your case, you would be better of building now. Many prebuilt computers leave you little, if any, room for upgrades down the road. Price a custom build and then head over to Dell and build as close to the custom build and the savings will be very little if any. Anyhow...we're here to help you...I'm sure someone else will come along and add some input.
Check out this thread for more info on prebuilt and building your own.
Hth...
e.n.