Re: 24" widescreen LCD running on ATI Radeon 9600?
I think it would be fine, depending on what you do with your computer. If its just internet, email, etc. the card should be fine. But, if you start playing games, the bigger screen will slow things down.
As for a pci e video card for under 150, i would say a 7600 gt. I personally have one and its great and can play most games pretty well. (Sorry, dont have any ati suggestions)
Also, for the ddr2 thing when you say you need ddr2 for a core 2 duo, you dont because I have a mobo that has both ddr and ddr2 and im using ddr with a core 2 duo.