Dell Studio XPS with i7 core?

That's a decent price if you need the monitor. The Dell motherboard bios' doesn't come with any overclocking settings. The power supply is usually around 350-405 watts. Dual vga support is too costly of an upgrade. Instead, order the video card separately from newegg and install it yourself. The 4850 should run with the standard dell power supply. If you don't need the monitor, you can sell it separately for a good price. Check the motherboard specs if you can before ordering. You want a standard dell atx board so it's easier to replace with a non dell board down the road if you need to someday. For micro atx, DFI just came out with one for $230 at newegg. It's the only micro atx x58 board so far.

Spend a Bit more, build it yourself, get the quality components that matter for the future of the upgrade paths (PSU and MoBo) and sit back playing with your own creation, It will always be better than a system built for you by dell.

You will get better value for your money cherry picking your components yourself and dont forget the free "upgrade in speed" that overclocking gives you which wont be possible with the dell machine.

There are always good deals to be had, some retailers sell certain items at a loss to attract customers, spotting these and building your system around this can help you out the other end with a real great system.