There has been much interesting discussion on the subject and seeing the sort of equipment in use by the Seti team the cost of suitable UPS's to cover it all will be very costly (and complicated). One possible alternate solution would be to use a xantrex/Trace true sine wave inverter/charger connected to a suitable amp/hour capacity of deep cycle (gel for low maintance) batteries. These systems are very well tested and where multiple systems are to be protected are probably the cheapest and simplest route. I am basically talking about the type of setup many off grid homes already have installed, where the primary source of energy is generally solar power but in this case grid power would replace the solar/generator input and the batteries would take the full burden in a power outage. Single units will deliver up to 5.5 KVA and can be stacked for added power or reliability.

http://www.xantrex.com/index.asp

The solar/alternative power news groups are also a good source of additional information.

Oh and I have no connection what so ever with the company and only use a charge controller made by them, my inverter is a Studer 1.2 KVA unit, also extremely reliable.

Also I realise that the team will by now have the solution in hand but for anyone else contemplating protecting multiple PCs, it is possibly more cost effective and flexible in the long term to consider this route.

Regards