So I realize that some people build entire systems around a certain graphics card(s) they plan to use.
For me it was quite opposite. This is the first system I built and I did it a little bit at a time over about 3 months depending on what was on sale at the time. I saved the graphics card for last because it seems like the technology changes the fastest and I didn't want it to be obsolete by the time I got done building. So far I have:
600 watt psu
Intel i5 750
8 GB DDR3 1333 ram
2 x 32 GB SSD in RAID0 with Windows 7 Professional 64bit
2 x 1TB caviar green in RAID1 for data storage
Avermedia A188 dual HD tuner card
24 inch monitor
32 inch 1080p HDTV
Everything is running stock speed ie no overclocking
I've heard a lot of comments that say a graphics card depends on what you use it for.
I plan to use my computer for three major things:
1) Use my DVR tuner card to capture over the air HD digital tv signals and then replay them on my 32 inch HDTV.
2) Use my computer's DVD player to watch DVDs on my 32 inch HDTV.
3) I am a photographer. So I use a lot of Photoshop CS4 and Lightroom 2. (I don't do any 3-D stuff though, don't know if that matters)
And this may or may not matter, but...
I don't play games ... ever. Especially not fast shooter games. Maybe the ocassional Age of Empires 2 or something like that once or twice a year.
I would be willing to spend up to $200, but if something cheaper will do the same for what I need it for then I'll go that route.
I had been looking at the PNY Geforce 9500 GT 1GB. The GTS 250 is also another one I've been looking at, but I don't keep up with all the video card terminology (pixel pipes, processor cores, etc. ) to know what anything means or what is good.
I wish I had more knowledge about photoshop, as that really is the application that will likely determine how high end you go. But out of the two cards you are considering, the GTS 250 is the better card.
I would encourage you to stick with the lower price range. You were right that graphics technology changes fastest--so buying a lot more than you need doesnt make sense. Another $50 card in 3 years will be better than the $200 cards available now. Get one with more ram on the card--it will be better for large displays+ graphic stuff.
I think nVidia cards have CUDA support, im not sure about ATI... that might be something to consider.
Also--This is total speculation, but because of Apples reputation in the Adobe world you might look and compare to see what's available in Mac Pros.. I am certain any of those configurations would be great with CS4.
Also search for photoshop on toms and see what comes up.
The first link tells you what features are supported by the GPU and also mentions the following requirements:
at least 128 MB of RAM--and a display driver that supports OpenGL 2.0 and Shader Model 3.0.
The second link has a few people talking about issues with Windows 7 x64 so you may want to check that out. I use Vista x64 with a 9800GTX and no problems.