4. ATI Radeon HD 5870 + 3x DVI->VGA Adapters + 1x Active (Powered) DP->DVI Adapter.
----------This will give you the max res of your monitors. But I'm not sure if it will work. Can someone Test to see if you can use a DVI->VGA Adapter off of an Active (Powered) DP->DVI Adapter?
probably not, the adapter would need to support analog signals which I see no reason for implementing in a converter when you can have the correct direct adapter
one thing though for the thread starter, I wouldn't personally buy any VGA only panel anymore, not future proof, worse quality, less functionality
also one precision for 58xx & 59xx series, two legacy (VGA/DVI/HDMI) screens are supported natively with direct or passive cheap simple adaptors , the third one needs a DP screen or a DP active adaptor (which was said already)