Also, the N52 is not scalable. It is USB so it would take some really elaborate hardware to multicast it - unlike PS/2 which is far far far easier as it is a dedicated protocol.

No reason to buy more than you need but I personally tried the N52 but never actually used it for any length of time.

Consider using Synergy or a dedicated keyboard for each machine if you are only going to two box. You could always purchase a vetra broadcaster but $200 is a bit steep for most people to only send keystrokes.