Why not go with a HP?? I have had both Dell and HP. My HP rocks. It's a true desktop replacement without the need for a "docking station" and I picked it up for $1k (hell of a deal @ Best Buy one day). I just saw a pretty decent HP in the paper last weekend for like $699 after rebate. If you can get approved by Dell then I'm sure you could do the same @ Circuit City, BestBuy or Staples. Just my $.02
If you are dead set on a Dell....Just get as much horsepower in the processor as you can afford.