Hmm...a 470 watt CPU should be fine for all that!
Does the Leadtek 3800GT have an external power molex connector it needs to be plugged up to? As well as in the AGP or PCI-E slot? Since this sometimes doesn't give enough power
Try looking for a connection on the card which one needs to be plugged into, and there should be some spare ones on the PSU.
If it is plugged up to one, try plugging it up to one thats not shared with other ones since thats a really powerful card, and other deivces might drain some of the power it needs.
I hope this helps