I believe you can have two nvidia quattro cards installed and each one can be split into two. I also think that one of them can handle four monitors but I am not sure about that.
As far as 'cheap' goes, that is another problem as i don't think that they are that cheap.
Never tried more than two displays from PC's theoretically 2x 6600gt's (about £60 worth) would have 4x dvi ports, but no idea if drivers support showing four screens in such a setup.
...and if you want to go even cheaper you could get 2xFX5200 PCI cards and run 4 displays that way. ...but you'd have no 3D capability worth mentioning.
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It's not just about how fast the rig is, its about how good the rig sounds.
Well, you either want to get a motherboard that can handle 2 graphics cards and get 2 graphics cards. The cards have to be capable of driving 2 monitors each. My 2 X 7600GT's can although I have never tried it. Or you could try one of these USB video converter things...no clue how well they work though.
http://www.usbgear.com/USB-Video-Card.html
what mobo do you have? do you have agp or PCI-e. if you have PCI-e do you have 1 or 2 slots? a 4 output Video card is not cheap. You are best off getting 2 dual output video cards.
If you're going for a one slot solution the Asus EAH 3870 X2 1GB is born with four DVI outputs allthough the $359.99 (newegg after mail in rebate) can't excactly be called cheap. matrox also have some cards that support four outputs, however they're all both more expensive and weaker than the card from Asus.
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It's the little things that do the big difference!
buy a 780G mobo with a HD3450, you could do Hydravision with that. With a small CPU, around 200$ for the kit (mobo, CPU, Ram and video card), assumng you have the case, power supply...
