First of all, your going to want to run the monitor that is displaying the finder on the primary display, or port one. Your second monitor will be on the second port on the Primary Card, and your third monitor will be on the second video card. I recommend this because if you need to use any thing else besides the finder well its on the third monitor, you will have to shut down what is on the primary display. There isn't really anything that you can call a "splitter" for video signals. You'll have to get a KVM switch, probably one for each monitor. If you have some cash, there are some around that will send the video signal on to another VGA port on the switch and to an s-video and composite ports. But don't forget these switchs only use VGA signals, not DVI. So if you are using an Apple LCD, you'll have to find some other monitors to borrow. Since you will need a second video card, shop around. If you look hard you can find the odd geforce mx 4 PCI that supports dual monitor and has the s-video in-out port. This will be the best bang for your buck. And if you are wondering about your number two choice, it does exist, if you have about three grand. There are a few pro cards that have 4 VGA or DVI outputs on them. And about number three, don't even bother with that. Setting up a second video card can be enough of a hassle, three just means you need to get out of the house. Although I am pretty sure OSX supports 3 monitors, I haven't ever tried it. So tell my how it works out!
SaVe A tReE, eAt A bEaVeR