If you have a good local computer store, recommend you consider having a computer built to your own needs and specifications.
Even if you're building your own system, it's great to confirm what components work best together for the results you want over the next four years or so.
After using various off the shelf computers such as Gateway, it was a huge treat to talk with local experts and have my first custom machine built just for me. The cost apparently was about the same as getting some of the best deals from Dell or Gateway.
If you don't have a good local computer store, I'd probably go with Dell, but talking first in detail with the most knowledgeable people I could find there for optimum customization.
Sorry if this is stuff you already know. I'm just so impressed with a customized computer with local expert input that I think it's a worthwhile reminder for everyone during inevitable periodic computer upgrading.