As the above poster has already said the Rating is measured in Wattage or W so as there is no country in the world that uses 275 Volts I'm assuming that you have a 275 W Power Supply which sounds about right for a Dell.
Anything that actually fits in the case and is of a greater Power Ratting will do the necessary job but as the above poster has already said not all Power Supplies are created Equal some are much better than others and at the risk of giving a skewed idea of what is best I personally only use Antec Power Supplies as well. These are rated to a Constant Power and are the minimum power that they actually can produce they will Peek out much higher for short periods of time.
So you can purchase a PS of the quality of an Antec that is rated to 300 to 350 W or a Unbranded one rated to 450 or 500 W that will do a similar job and provide the necessary power. What is a good idea of how good a PS actually is, is when you connect one to a UPS with the same or similar Rating a 350 W Antec PS will constantly drive a 300 W UPS over the edge but a 550 W Unbranded PS will work normally and not cause the UPS any problems. Sorry I can not suggest any other brands as I'm in AU and only buy these from 1 Wholesaler because the rest are rubbish which are not worth what I pay for them let alone the Retail Price of the things.
I'm sure that there are other brands that are as good it's just that the suppliers that I buy from don't sell them so I only use Antec for this reason. They are considerably heaver than Unbranded Power Supplies and have superior everything inside them from Better quality Heat Sinks to Fans and electrical components. The down side is that they cost more than the cheap units but I consider this money well spent as you get much better protection for your Data and when it's all said and done the Data is what is the expensive stuff on any computer. Everything else can be replaced in an hour if necessary but recovering Data is horrendously expensive if the user doesn't have a Backup that isn't constantly connected to the computer. It also takes much longer to recover that it does take to replace the hardware.
OH BTW I'm nasty it's HAL 9000 who's the Nice one. ;)
Col
[i]edited[/i] because I'm an idiot as well and can not tell the difference between a r and a d.
