Budget for a server why not go buget pc...
I'm a recycler/refubisher.
MS does W7 and Office 2007 licences charities etc for $6 USD each via its Citizenship licenses.
We just bought some ex corporate Lenovo X61 laptops (Core 2, 2Gb, 80Gb HDD) for £20 each
So for £1000 plus labour, you could have a W7/Office equipped core 2 duo for each user. WAY cheaper than a go faster Server 2012 piece of tin!
Contact your local MS Registered refurbisher....