connecting 3 monitors to ATI Radeon HD 5770

I'm looking to add a 3rd monitor to my HD 5770. I've read up on the issue of connecting 3 monitors to this graphics card and I think I get it, but I want to make sure before I buy any new equipment. I currently have:

1 monitor connected directly through DVI

1 VGA monitor connect with a passive VGA > minidisplayport converter

The monitor I'm planning to buy has a displayport connector. So, am I correct that in order to add this monitor and be able to run all three simultaneously, I would need a standard displayport > minisdisplay converter for the new monitor, and to replace the passive VGA converter with an active VGA converter? If I were to add a VGA extension cable to the mix, could that cause any problems? The point of this process is to have my older, smaller monitor be able to be moved several feet away from the computer as part of my home studio setup.

Thanks.