Mono blocks wiht preout/main?

Is it possible to use pre out/main in to run monoblock amps. off my NAD reciever?

I have been on the Channel Island web site but notice the D 100's only have one RCA connector on each amp.Would the cable go from the preout to the amp using this connection?

If this is how it's done the main in would remain empty and the jumper would no longer be there.
You are correct. When you remove the jumper you have disconnected the NAD's amp and when you take an IC from the RCA of the pre-out to the D100's you have effectively replaced the amp in the NAD. Mono amps only need one RCA. You run an one IC from each pre-amp out (L&R) to the appropriate (L&R) amp. Don't forget to disconnect the NAD from your speakers.
Correct, the main in would be used for an outboard preamp,'s an input. The jumper is the link between the preamp and the amp section of you receiver.