Keep in mind that you can only install one display driver per windows installation, so both of the cards have to be from the same company, and support the same driver versions.
Also, be sure that when you have 2 graphics card in your computer, your motherboard doesn't split the PCI-E lanes into two x8. (this usually happens in cheap Motherboards less than 130$). It can affect your good GPU's performance very badly...
You can't run games on those three displays, since it is two separate GPUs.
You can spare your money if you already have an intergrated display chipset that can work alongside your GPU.