Is it possible to use another video card into iMac 24" 2008? I have an iMac 2.8 from 2008, all works like a charm for now, but I'm lacking some GPU power from my ATI Radeon HD 2600 Pro.

I checked on google and think it's a PCIe x16 card yet can't find anyone saying that upgrading this component is possible.

From the detailed info's, I can see that's plugged in by and PCIe x16, is it possible to upgrade this video card?
The 2008 iMac's use MXM Video cards. You could replace it but it's (very) expensive for not much more performances (High end models used a 8800M GTS (branded as a 8800GS).