Understanding impedance: amps and speaker cabinets
So I'm trying to get rid of my guitar amps. . . four or five combos. . . and get down to just a few heads (orange, mesa, fender) and a couple of 2x12 cabinets. I have a little home studio (like the rest of you), and I wanted to keep all the amps in the control room with me for tweaking, then run speaker cable to the cabinets in other rooms. This way I can tweak the amps without walking from room to room, and also I can monitor what is actually going to tape.
So as I'm setting this up, it occurs to me that I don't have a full grasp of the choices for impedance coming out of the amps, and the different impedance inputs coming into the speakers.
Help me understand this.
Specifically: If I'm coming out of one amp into both cabinets, do I need to use the same impedance outputs to both? Also, does the length of speaker cable affect my choices (it will probably be about 30 feet to each cabinet)?
I've been playing guitar for 25 years now, but I've used combo amps almost exclusively, so this is a topic that has somehow eluded me for a long time.
Thanks in advance for your replies.