We had a similar problem. In the long term you need to look at efficiency vs. installation cost.
Running one (or two) large units constantly just for a server room is in the long term quite expensive depending on where you live and how much the cost of electricity goes up. Unless you are in a facility that is staffed 24/7 (and I suspect you are not) there is no reason to do this.
For between $1800 and $3400 you can have a "mini split" system installed which will cool only one room, on its own thermostat and be completely self contained. It can be installed with a small pump to dump moisture out close to the external unit. With a cooling (compressor on) current of 9-10 amps, and 12000Btu of cooling, we are able to keep our (admittedly small) server room at around 65F, which gives more than enough response time for a unit malfunction before the temperature reaches critical levels.