AGP GPU - Business v. Gaming Use

Surely someone' s explained all this . .. I just can't find it. Two questions, really:

1. Graphics cards for Business use vs. Gaming use: It seems like all graphics card reviews now are based on gaming performance. We need to understand the relevance of those comparisons -- if any -- to making decisions about purchasing video cards for business machines to improve performance over the integrated Intel Graphics originally provided in our P4 3.0 AGP systems.

Our basic machines are Dell GX270 towers; some of these have been maxed out to 4GB RAM, & -- because we've been told that the stock 250W PSU is too weak to support a separate videocard -- the stock 250W PSU in some has been replaced with PC Power & Cooling's 410W drop-in replacement specifically to support installation of new video cards.

Of course, we don't support our people gaming at the office, but our people do need to be able to deal with photo and video software, both for viewing and editing; so we are interested in video card performance from that perspective and, of course, for any other business performance benefits we can achieve.

In short, we know that upgrading from the integrated graphics (stealing CPU resources & memory from the main system) to getting separate videocards will give us a performance boost, but we just don't know whether paying a bit more for newer/faster graphics performance makes any difference for business uses or, if so, how and to what extent.

So, some sort of basic explanation about evaluating video cards for business use vs. for gaming use would REALLY be helpful. That would include:

Is there a correlation between gaming graphics performance and business or should we be looking at something else?

Are there any specific uses we can make of standard graphics cards reviews in trying to decide which cards/GPUs would be the best choices for us?

What should we know about nVidia v. ATI for business performance or stability?

And what about the improved heat performance of smaller chips (e.g., 55nm vs 90nm - or whatever that measurement is) vs. head to head graphics performance of the chips? Seems like we could get by better with a newer, smaller chip that has the same performance as an older, larger chip, just from the standpoint of PSU requirements.

2. Suggestions? The obvious next question is -- does anyone have suggestions as to specific cards/GPUs we should be looking at for these GP systems? If so, what are they and why do you feel they would be good choices for us? We'd like to have dual-DVI outputs, if possible.

3. I know, I know. Everyone's first reaction is to get all-new systems. That's not an option for us now; but some hardware upgrades are. RAM, PSU, & videocards are OK'd, so we're trying to figure out the best choices for now.

Thanks,
pdalton