Updating Gateway GT5656

[TDavis50]

I got a Gateway GT5656 desktop about a year ago, and want to upgrade it with some newer parts, particularrly a 10/100/1000 ethernet because my school gets T1. What parts are compatible with this desktop? Here is the spec sheet:
http://support.gateway.com/s/PC/R/1015002R/1015002Rsp3.shtml

 

[A Cheese Danish]

Any ethernet card that has PCI will work. Also, any card that takes PCIe x16 will work.
And, I'm pretty sure, almost any processor that uses an AM2 slot will work
But you will need to upgrade your power supply.

 

[TDavis50]

What power supply would be sufficient for adding the 8600 GT, and another hard drive?