well you could do it like that, but you will have too monitors looking good and the other one just not, Your much better off using a SLi or crossfire motherboard with two decent graphics card its, and have the centre monitor on its own car as thats the one you will be using the most, dont see any reason for it not to work.
AMD x2 5000+ black edition at 3.3GHZ zalman cnps 9700-NT
Gigabyte GA-M57SLI-S4 motherboard
3072mb: OCZ ddr800 gold
2x 7800GTX in SLI for 20" viewsonic
OCZ 600watt power supply
- plug for my gfs site