6 monitors is a bit niche, probably, and I wouldn't - for one - want to pay the electricity bill. (The bill on just one 30" monitor is enough! That's why I went 24".)
I'd eventually like to have 4 24" screens (3 side by side + a touch screen in my desk that mirrors the middle screen). A single card solution would be good.
There was a 3870x2 (expensive, power-hungry) that had 4 outputs.
Further, Hexus (or was it Tom's) showed 780g + ATI discrete card driving 4 displays.