RedneckDude - In that case, get another nvidia card to run the other monitor. I have a GTX 260 for the primary and a 8800GT running my other two monitor, but you can use a cheap card if you want. Unless your trying to do multi-monitor gaming. I have a second rig with two t$30 cards and they work fine if i ran three monitors, which I do sometimes.
Also you can get a USB to VGA adapter if you want, I did that one time using USB 2.0 VGA Adapter
Good luck, keep me posted !
Mirau - I suggest that you do one of the following
The 5870 has either (1) 2xDVI 1xHDMI 1xMiniDisplayPort or (2) it has 6xMiniDisplayPort
In either case you should be able to connect 3 monitors easily. The card that has the DVI connector, I believe you need to use the MiniDisplayPort for the third monitor. I think the DVI and the HDMI share that same connection to the GPU.
In either case you need to make sure your monitors have the MiniDisplayPort connector.
If this is not the case than i suggest to you that you replace your secondary card with an ATI card and use this card to run the secondary monitors. Make sure that the 5870 runs the middle monitor and the other ATI to run the other monitors.
Running ATI and Nvidia driver on the same machine can cause strange things to happen. I have seen some of my users have a whole slew of issues because of the mix drivers and I have also seen users with absolutely no issues. I have also seen people have some really strange issues because of the mix drivers. From the sound not working to resolution for all monitors limited to 640x480. I have also seen where one monitor would have the limitation and the other monitor not.
Good luck keep me posted :!!!