Help in upgrading Dell Dimension 8300 Power Supply

[Juanra]

I'm thinking of upgrading my power supply. I'm pretty sure my PC does not have a propietary power supply (bought early 2004), but the back side covers the on-off button found in many power supplies, such as this one:
http://www.antec.com/us/productDetails.php?ProdID=23500
Picture of backside. Notice it covers most of the power supply.
http://www.billigdrucker.de/images/hardware/komplettsysteme/dell/dell-dimension-8300_back.jpg
I know I have few options. 1) Upgrade to the PC Power and Cooling one, shown here:
http://www.pcpower.com/products/viewproduct.php?show=S41D2
2) Open a hole in the back of my case to be able to fit other power supplies.
What do you guys recommend?

 

[Tmagic650]

Pick your supply from here:
http://www.pcpower.com/products/power_supplies/selector/dell.htm

Dell still uses proprietary supplies. Don't make a mistake