I'm afraid I don't have an exact answer to your question, but I bought a new computer in May. I'm a software developer and not a photo-professional, but I use my computer a lot and want good picture quality both for long hours in front of the screen(s) and for some image editing.
My previous PC had a Matrox P650 AGP board which I was happy with. It has almost no 3-acceleration but support my dual screen setup with one 20" and one 24" monitor. Both are connected with dvi, and the P650 support either 2 DVI or one DVI and one VGA screens.
Unfortunately my old board couldn't be used in my new PC with PCIe-interface, but the P650 is (still) available and now also comes with as a PCIe-card. Unfortunately it's fairly expensive (not compared with high end "games-cards", but compared to other boards with similar 3-d performance). The AGP-version was without a fan but the new version has a fan (I've haven't found info about noise, but assume it's not that bad as the old version managed without a fan).
I also asked questions similar to yours, and got some answers, but nothing that made for an easy conclusion.
So I searced on the web. Found two articles (could dig up links) about DVI-performance on Nvidia-boards not being as good as on ATI-boards, but they were published at least two years ago and I decided to keep Nvidia as an option.
I looked specifically for double dvi-boards, preferably without a fan and with some 3d-acceleration (in case I wanted to use the new Vista interface when it comes out).
Not many boards had double dvi ports and no fan, but I found some and just before I had to decide Nvidia came out with the 7600GS chips. These boards fit my requirement well, with an up to date technology and low to mid level performance which mean fairly low power consumption. Several manufacturers launced 7600GS boards with passive cooling, and I got one from XFX (the only 7600GS-card at the time with dual dvi).
It works well so far, can't se any difference from my old PC with matrox card and support dual screen with high enough resolution for my system. Can't say that the picture quality is better or worse than other cards, but at least it's a fairly cheap card and completly silent.
Someone commented on Nvidia vs Ati dual screen support, and I must say I prefer the Ati version, but it's a small issue and I wouldn't let that be a deciding factor.