Hey guys we are planning on replacing our old UPS because it only last for about 15 minutes during power outage.

The ff are the device load for the UPS:

5 IBM Servers (DC, File server, test server etc)
2 Switch
1 Firewall
1 Router
1 Modem
1 Monitor, Keyboard and Mouse
1 KVM switch
1 External HDD
1 Extra linux test server
(will add another device in the near future)

Can somebody recommend what vA should I need. I'm not very technical when it comes to this i cant even compute the load of the server. Based on the devices above, what is the best spec for a UPS preferably APC. Can somebody explain the volt ampere? will it last long if it's high? I need a UPS that will last 1-2 hours at least

Input is 220-240 v / 50-60 Hz and output is the same.

Thanks!