The ATI HD 5XXX series doesn't have all DVI outputs, but it's probably the best solution for what you're looking for. Having dual video cards will allow for up to 4 outputs, but you won't be able to render a game or something intense across all four.
Sounds like your best best is the ATI, and if you're going to be buying monitors, try to get one that can take display port. it has 2 DVI, and a display port. It also has an HDMI, but from my understanding, it's one of the DVI OR the HDMI, not both.