I currently have 5 displays. The following is how I installed them.

1. Three 19'' for workspace. One of them is connect directly to the graphic card via DVI. Two of them are using usb graphic adapters.
2. One 720 projector - directly connect to the graphic card via DVI.
3. One 30'' dell monitor - currently connect to laptop via VGA.

I would like to connect 30' dell to my main computer. 

I do not game or use graphic applications.

What would be my best options? I am thinking to buy two lower-performance ati or nvidia cards and install them as crossfire(???) or sli. Am I thinking correctly?