So, I think I'm going to need at least a 550W power supply...
I have a X1900XTX, X2 3800+, 2x1GB DIMMs, DVD+/-RW, 4 USB devices, and a SATA harddrive.
http://www.extreme.outervision.com/psucalculator.jsp
According to that calculator, looks like I won't be getting off cheap.
SO...