Standalone DC power recommendations?

[Deepak Jain]

We are going to need to deploy about 800A of -48VDC power equipment in a
datacenter that doesn't supply DC power normally. They will give us an 
three phase AC-power feed that is generator backed.

Can anyone point me in the direction of a decent vendor of DC-power 
plants that are suitable for this size need and/or a ballpark price one 
would expect to pay for the equipment?

Thanks in advance,

Deepak