The questions that need to be answered are:
When you receive your systems, do they come with a restore CD and are they, if you turn them on, preinstalled?
Are the systems you receive, more or less, the same system?
Are the systems you receive SLP keyed
If you where to use the cd do you have to enter the key or not; if you don’t need to enter a key, you’re systems are probably SLP keyed.
The reason these are asked is I can tell you a simple answer. If the systems are SLP keyed and have licenses for each system, you can upload an image of one system, and push that image to all clients of the same make and model. No Sysprep or anything.