High_Flyer,
I made the mistake of expecting the 9600 to work miracles too when I first bought one. Compared to what video I WAS using before then.... it seemed like it should be a WORLD of difference. I expected it just HAD to fix the various framerate issues I was having.
I installed a 9600 pro (which is 128 M of video RAM) on my old 2.4 gig P4 w a 533 fsb and 1 gig of ddr RAM. Surprise, surprise...... it didn't cut it with FS2004 where it really matters... short final at a big international airport with lots of AI and eye candy running.
I now have upgraded the whole machine to the specs on the trailer below...... and it STILL is no screamer by any means... but it is FAR better. I can live with this. But I STILL can't max out everything that FS2004 has to offer.
Up away from the ground and the AI and so on........ 70-80 fps and smooth as silk. Of course.... there is no demand on the system there.

Now at least with MOST stuff in FS2004 maxed..... I can sustain 30 FPS in the demanding scenarios.
You for sure need to go up to at least 512 M or RAM..... preferable a gig. But don't expect geometric or exponential increases in performance... they are more "incremental" improvements.
You can also consider investing some bucks in Ramsa's machine tuning service to get the most out of what you have......... which a lot of people swear by.
You are not alone in "the search".
best,
.................john