I advise you not to get a Dell. Not only do their machines seem to be substandard, but if you <i>ever</i> need anything that involves the word "support" or "warranty", you're out of luck, because they're less willing to help you than Microsoft tech support (and MS charge you $75 for phone assistance).

The way I would go is to look for a small computer vendor in your area (they almost invariably sell parts around 25% cheaper than big stores (in New Zealand anyway)), and get them to assist you in building a PC. You won't have to build it yourself, and they'll help you choose the parts you need for the lowest price.