Materials

For multiseat you need more graphic cards, you will need a graphic card for each monitor.
You will also need to have a keyboard and a mouse for every seat. It is the best you use all the same material for multiseat, this gives it a better look. There are even companies specialised in multiseat computers and construct special tables to make a good looking layout for your multiseat. Eg. You could put the central computer in the middle of a round table and you place all monitors around the central computer.

Source: http://www.multiseatcomputer.be/