Not sure if Nuendo has it, but Cubase has something called VSTLink, it ties 2 machines together with sample-accuracy. Just takes one digital audio connection between them. I do it with just a S/PDIF connection, and then I use the lightpipe connection on my 2nd machine to bring audio back to machine #1.
If Cubase has it I'd guess that Nuendo does too. It's pretty cool, the 2nd machine locks right up perfectly to the 1st.