Hi all, I'm new to this site.  Up until this week, I've been completely oblivious to ohms.  I'm a Marshall guy, who has a Marshall JCM 800 2555 head and 2 JCM 900 cabs (angled and straight).  This is a great amp, but it's a one trick pony.  Two years back, I was blown away by the Line6 Spider Valve HD100 and I had to get it.  I've used it quite a bit with my Marshall cabs.  Up until now, I never thought anything about ohms (stupid I know).  I've been reading some discussions on here and now I'm concerned about having it hooked up correctly.  I know the "buy a Line6 cab" will be said, but I like my Marshall cabs and want to make sure that I'm hooking it up correctly.

The back of my Marshall cabs have a 4 ohm input and a 16 ohm input.  The Line6 head has a choice of 4 ohm outputs, 8 ohm outputs and a 16 ohm output.  I have some pictures included below so you can see what I'm looking at.

My questions are:

1.) What is the proper way to connect the two when I am using one cab as a half stack?

2.) What is the proper way to connect thew three when I am using two as a full stack?

Again, this ohm thing is somewhat of a new revelation to me and your help is greatly appreciated.  Thanks in advance!