I'll try to keep it safe and just use the clone tools over ethernet while I sleep at night.

The EmpegClone utiilty is USB-only, but if you're running it overnight, then it's no big deal. The other option is to use Mark Lord's FTP kernel features to copy all the FIDs from one player to another, but that's more complicated.

Note that if you use the EmpegClone utility, the current Beta version doesn't work very well, so you should use version 1.03 final to do the cloning (meaning the players should be at 1.03 final as well).

I noticed the post about cloning to a higher serial number, what's up with this? Is this a bug, hopefully fixed with the next version?

It's not a bug, however it will be fixed in the next version anyway.

The clone tool was originally written for Mk1->Mk2 upgraders only. But if you're getting five units in a row, then you just make sure to load the music onto the lowest one first, and use it as the source for all the clones.

Note that you'll want to get the tags right on all of the files before starting this whole process and before sending any of the files to the first player. (See the FAQ for more details.)