Looking for a good PSU and video card combination

[Labyrinth]

I've been searching for weeks now trying to find the best way to go about upgrading my graphics and I'm still pretty much at square one. My computer specs are as follows:

AMD Athlon 64 X2 Dual Core Processor 5200+ 2.7GHz
4GB DDR2 SDRAM
640 GB SATA Hard Drive (7200 RPM)
Optiarc DVD+/-RW AD 7200S
Windows XP Home Edition
Radeon HD 2400 PRO
Dell E198FP 19-inch monitor (VGA only)

If I missed anything, it's all the default options for refurbished Inspiron 519s in the Dell Outlet (if that helps at all). For some reason, I can't seem to figure out what PSU is in there now, but I assume it's not very powerful.

Anyways, I'm looking for a new video card and a PSU that can actually handle it without risk. I'd like to keep the price below $100 unless absolutely necessary. This computer will be for moderate gaming, as in I won't be trying to play Crysis on max settings or anything. I'd just like to be able to play some newer games. I also have no plans for overclocking since I have no idea how. Cards I've been looking at are the ATI 3870, ATI 4830, and nvidia 9600GSO so I don't really prefer anything specific, just as long as it plays games relatively well and won't cost a whole lot. Same goes for the PSU. I've seen mixed opinions about some of the cheaper ones, so I wanted to make sure I wasn't getting a piece of junk.

Opinions are welcome. If you need anymore info, I'll do my best to get it to you. Thanks in advance for any advice.