Using an iMac 27 inch as external monitor

I am thinking about buying an iMac 27" to use both as a desktop in it's own right but also as external monitor for my PC rig with which I presently have two 19" monitors. There seems to be some confusion as to which graphics card you need to have in your PC to make this work. I have a Gigabyte 5770 card today, does anyone know if this card will work?

Any card will work you just need a dvi to mini display port converter box

Amazon.com: Atlona AT-DP200 DVI to Mini DisplayPort Converter: Electronics

Ramimac1 said:

Any card will work you just need a dvi to mini display port converter box

Amazon.com: Atlona AT-DP200 DVI to Mini DisplayPort Converter: Electronics

Click to expand...

The Gibabyte card has a Display Port, isn't it enough with a display port-to-mini display port, rather than the converter?

I would think that with a display port to mini display port adapter that it would work.