Been a long time I heard about PCI-X ... but why is your boss running on a server, as its the only place where you usually find PCI-X slot.
Still to answer your question, Yes, there is PCI-X video card, but there is not a lot and the price are pretty high ... if you are lucky enough to find some in stock anywhere. If you are lucky and your PCI-X slot is backwards compatible (most are to PCI 3.3v, but not PCI 5v cards) then you can install a PCI (most likely 2.2 / 2.3) video card as an 'upgrade'. From a fast research online, I could not find any PCI-X card that will support 4 monitor.
What i would recommend you to save a lot of money is to use an external video card ... especially for a 3rd display.
Something like EVGA UV16 should do the trick for pretty cheap
http://www.ncix.com/products/index.php?sku=29798