Hi KaliNtheReD,
If you don't want to upgrade your motherboard to PCI Express, then you can stick with a good AGP card. One of the best value AGP cards out there would be the NVIDIA 6600GT series.
If you consider what is important in graphics cards, you will know that
core clock, RAM clock, memory bandwidth and pixel pipeline are determining factors.
A quick comparison (from various net sources) does in fact show that the Geforce 6600GT has a faster core clock and RAM clock than the competing Geforce 6800 Non-Ultra series and the Radeon 9800XT series. Memory bandwidth and pixel pipelines are lower in the Geforce 6600GT than the Geforce 6800 Non-Ultra.
Price wise, the Geforce 6600GT is cheaper than the Geforce 6800 Non-Ultra series and the Radeon 9800XT. The Radeon 9800XT is the most expensive.
What does this mean? Well, if you like to play 3D games, you may want to pay slightly more for the Geforce 6800 Non-Ultra series of cards. Although the 6600GT AGP has a faster core and RAM clock, the lower memory bandwidth and pixel pipelines means that it will slow down (compared to the other two) when used with high resolution 3D games, with maximum detail turned on.
On the whole, the Geforce 6600GT series of cards would cater to the mid range videocard buyer.
Although the 6800 will definitely provide slightly better performance, the 6600GT is quite a powerful card for its price range. If you own one of those older AGP cards, like the MX or 5200 series - the 6600 GT is definitely a worthy consideration.
What's more, the 6600GT is one great overclocker of a card. You can clock the default 500/900MHz to about 562/1030MHz without much problems.
In your case, given that you don't want to upgrade to PCI Express yet, and are looking to upgrade from that 'craptacular GeForce FX5200'
- I'd say go for that 6600GT. Brand wise, I think the
Gigabyte GeForce 6600GT or the
XFX GeForce 6600GT are both good buys. You'll do well to consider those 2 models.
Hope this helps!