I'm also in the market for a new graphics card (SH4 gives me 5 to 7 FPS

) so thank you for starting this thread.
The advice I got from DivingDuck is:
'a new gc will definitely do the job. I assume you need an AGP card, donīt you? The fastest AGP I know is an ATI X1950 Pro @512MB DDR3. Should be a available for less than 150,-EUR'