for the +12v calc, I usually choose cpu/gpu/hdd/dvd/2 fans (or devices that load up the +12v only, memory / system board loads up the +3.3v / +5v rails). So...
eXtreme PSU calc[/url]"]System Type: Single Processor
Motherboard: Regular - Desktop
CPU: Intel Core 2 Duo E6420 2130 MHz Conroe
CPU Utilization (TDP): 90% TDP
Video Card: NVIDIA GeForce 8800 GTS 320MB
Video Type: Single Card
SATA HDD: 1 HDD
DVD-ROM Drive: 1 Drive
Fans
Regular: 1 Fan 80mm; 1 Fan 120mm;
Keyboard and mouse: Yes
System Load: 100 %
Recommended Wattage: 253 Watts
But, don't forget to subtract the "no load" system board wattage of 38w
253-38=
215w or 17.9A at most on the +12v rails combined.
Pad that at the 80% mark, you want minimum +12v@22.4A on your PSU.
The truepower 430w should handle that w/o an issue if you can get it cheap. Go w/ a 500+ unit if you have the budget, they usually handle +12v@35A or so - then upgrades and longevity are part of the consideration.