i dont have answers to your hdmi related questions, but I might suggest to look at at least 9600t or preferably 9800gt and with at least 512mb gddr3 RAM. 9500gt is slow and ddr2 is slow too. 1gb video meory on this card is frankly worthless (read, it cant ace crysis) - except may be for running two displays of the 2560x1600 resolution you mentioned along with vdpau decoding of 1080p. as such, even my notebook with 8400m gs with 256mb (128mb dedicated) will do 2560x1600 but runs out of ram for vdpau when using two displays.
I agree that the additional memory, cheap as it may be, is not going to increase performance much -- though it should help with triple-buffering, and many large texture maps (google earth?). Interesting about the vram maxing with 2 large displays. At least nvidia has dual display support, I don't think ATI fglrx does!
I had a FireGL 5000 (HP nw8240) running linux, and getting s3 suspend to ram to work was practically impossible, and ATI had poor/no support for many X features... Have been using nvidias binary driver since it's first release without half the trouble.
It's low power consumption, low heat, and low noise, coupled with great outputs (I need DisplayPort for my 2560x1600 30" 3008WFP display), make the card seem a good choice for general desktop work: qt/kde dev, graphics processing, vdpau, XV video, x compositing, and some OpenGL.
My problem is the ATI fglrx drive is a lot worse than the Nvidia binary drivers. The ATI driver won't compile/install well with the current kernel 2.6.28, and doesn't seem to enable the DisplayPort so I have to use DVI -- thicker cable with no audio.
Yes, I would buy an nvidia GTX 285 if it could be made to run at 50W the 350days a year I wasn't playing Crysis. That said, I wan't a quiet card too!