ATI 4870 In a Dell XPS 430?

I want to put an ATI 4870 HD in a Dell XPS 430 w/ a 375W PSU. From everything I have read so far my PSU will probably handle that card, and that the Dell 375W PSU is, in most cases, a lot better than a cheap 500W PSU. I would rather not have to replace my PSU since it voids warranty. What do you guys think? Please give me any other options or suggestions.

Current specs for the XPS 430:
* Intel Core 2 Q8200 Quad-Core (2.33 GHz)
* 3GB DDR3 Memory (I plan on boosting this to 6GB)
* ATI Radeon HD 3450 256 MB


I also picked up on this review (http://arstechnica.com/hardware/reviews/2008/06/ati-4800-series-review.ars/7) at Ars Technina that shows the full load power consumption at around 233W, but on the ATI web site they say a minimum of 500W is required.

Never mind, I decided to wait it out untill the 5750 drops, which should fall right in line with what I need. It will hopefully require only a 450W PSU and 1 6pin connector and provide a lot more power.