New Inspiron 518 in need of overhaul

Hello I am new to the community,

My boyfriend and I recently came accross a great deal on the Dell website and bought ourselves a Inspiron 518 with a Pentium Dual CPU E2200.My boyfriend loves gaming and wants to turn the system into something a little bit more capable of handling his favorite new games.

The Inspiron came with 2GB of installed physical memory but shows up as just over 4GB of virtual memory which I'm lead to believe means that we are running on on Vistas 32-bit version. The Inspiron also comes with a 300w power supply which I've found can be a little low for many modern graphics cards, the machine comes with only onboard graphics.

My boyfrind having replaced his own video cards and RAM previously has decided he'd like to upgrade the system with the following.

A larger power supply - APEVIA WIN-500XSPX 500W ATX12V / EPS12V Power Supply

More RAM - A-DATA 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory

and a mid-line Graphics card - ZOTAC ZT-98GES5P-FCP GeForce 9800 GT 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported

Before he spends all his money I was hoping for advice over whether or not his plan held any merit. Would these devices be compatible with the hardware we're already using and what kinds of issues can we expect with installation? Any ideas or advice are extremely appreciated.

Thanks

-PandasGirl