Wait until early May. The HD4750 will retail for under $100, play Crysis at 30fps on Medium settings at 1920x1200 (almost HD4850 performance), and be a much better offering than anything in the ~$100 segment today (faster and cooler).

http://www.anandtech.com/guides/showdoc.aspx?i=3538 recommends you wait too.

IMPORTANT: Make sure you current card uses a PCI-Express and not an AGP slot. If it's AGP then almost no current graphics cards will work in it (your best option would be an AGP HD3850 if you can find one). Also, for a system with an AGP slot, your CPU won't be enough to handle Crysis anyway (no single-core can).

I believe my old athlon 4000+ with 7800gt could just barley handle medium settings :P

I'm pretty sure he mentioned his existing card is an x800 (PCIe)

What you really need to look at is if your power supply can support some of the higher end video cards.  If you buy a video card that requires the additional power, you may be required to upgrade your power supply at the same time.

He said it was an X800 XL, yes, but there are AGP versions of that out there. Actually a bigger concern is the CPU: if it's a single-core Pentium 4...

for your price I'll advice you to get 8800 GT its specification is the same as the 9800 GT you can even check nvidia.com plus I have it and I play Crysis on high settings and AA x2 AP x2 with no glitches or stater. and I think you can find a used one on ebay.