XPS 430 changing power supply

I'm wanting to upgrade my power supply in my dell desktop as I plan on getting a nvidia 460 or amd 6850 graphics card to replace my current one and as such I need to upgrade my stock 375 watts dell power supply.

Having done a bit of research on things that are compulsory for a dell case I came across this PSU http://www.overclockers.co.uk/showproduct.php?prodid=CA-055-OC and I was wondering if you could tell me whether or not it would work in my system :)

Just as an FYI as well I'm not very knowledgeable when it comes to power supplies so you will have to forgive my lackluster responses to anything you may ask me as I just don't understand it :P