The only thing I would change in that rig is your video card. It's horribly outdated. PCI technology for video cards is, well,
dead. I recommend that you invest in a better video card, and failry quick.
I recommend about three cards, all of which are DirectX 9 compatible and perform rather well.
The first up, is the 7300GS. It's horribly under-rated simply because it has 4 pixel pipelines,
however, it still uses a 7 series GPU, and from reviews, it even plays Half-Life 2 and Call of Duty 2 on max settings, not bad for a video card that has four pixel pipelines and only cost $70.
The second is the ATI Radeon X700. It's about $25 more then the 7300GS, but not quite as good. I own the AGP 8x version of the X700 and I can honestly say it's at the bottom of the mid-range video cards. It's somethign you'll want to consider gettign only if you want half-arse performance, and just to play the game.
The last video card I recommend is the NVIDIA 6600GT. This is about the same price as the X700, yet it delivers a tad bit better performance, and includes a different type of RAM, GDDR3, which is just Graphics Double Data Rate RAM 3. It's much better then your standard DDR on most video cards.
Whichever card you get in PCI-Express, it's sure to be better then that NVIDIA 5500. I sugest you either upgrade to a low to mid-range card now, or save up some cash and upgrade to a much better video card in the future. Which ever card you decide to get, wether it be a 7 series NVIDIA or an X1K from ATI, it'll deliver all the eye-candy you'll want.
But be forwarned that if you want to have the absolutly best graphics available, then you should be willing to spend up to $400-600 dollars depending on what kind of performance you want to get. If you want all the eye-candy enabled and not have to upgrade for years, then the $500 cards are the ones to get. That may seem liek a lot now, but when everyone has to upgrade and you don't, in the long run you save yourself money.