I'm not sure you'd have enough power with your 800A 480V setup to drive the 5PH of gear.  If my math isn't failing me (it probably is, so I apologize in advance if I screwed up my calculations), that setup would give you total available power of 664.32kVA.  If you could covert that completely to 208V power, it would give you 1846A at 208V.  Even if you could get that at a 0.99 power factor, that would give you an absolute total of about 658kW.  5PH of S7s would require about 1.25MW for the gear alone.

Just food for thought..