Matrox Parhelia if your willing to pay the rather considerable price to get the best quality, feature set and versatility.
You can get a G550 at a much cheaper price though, and it'll offer the best 2D visual quality available short of the Parhelia, and pair it with the most versatile multi-monitor feature set available.
The downside being of course that the G550's 3D performance is quite poor.
If you just want a cheap solid board would good 2D and a good multi-monitor implementation, then the ATi Radeon VE is quite attractively priced. Though again, it's 3D erformance leaves much to be desired.