At my last job, we had a more typical pairing setup with one machine (27" imac) in the middle of two programmers. When I paired with a non-Emacs user, we'd put Emacs on my half of the screen and their editor (usually Vim, occasionally Textmate) on their half.
The only caveat is that you have to make sure your editor will refresh files when they change on disk. That way, when your pair saves a file, your editor reflects the changes.
Textmate does this automatically; in Emacs, you may have to put
(global-auto-revert-mode 1)
The main downside is that you can only fit half as much code on the screen, but this can be mitigated by using a sufficiently large screen. In my experience, a 27" display is sufficiently large and a 24" is pretty good, but anything smaller starts to feel cramped.
It also provided both of us with the ability to see the others changes.
It's fun and almost LAN game like in terms of having everyone create stub items, then others go in and fill them out, then someone else goes in and further adds to that given item, etc etc.
BTW, Etherpad was released as an open source project (https://github.com/ether/pad seems to be where the development lives) as part of the acquisition and there are tons of clones out there if you still want to use something simply with no sign-in, etc.
Check out: http://piratepad.net/ep/search or http://typewith.me/
Not quite the same as a collaborative editor, but similar.
In this vision the two person aspect is inescapable. The issue is when does the second person say "Whoa! Dude, that is such an obscure way of writing that, no-one will ever understand that piece of code." Do they say it when you have just typed it in and can be persuaded to play about a bit, searching for consensus on what makes for clear code. Or do they say it when it is too late?
There are people I like to pair with and people I am not as productive when paired with.
Try to pair with someone you like.
For a while, we had a couple people who really liked pair programming at work. Our desks really, really weren't fit for that. They went through a lot of things and finally settled on 1 person having the work computer, and the second remoting into it. They would sit at their own desks, which were close enough to talk, if loudly.
Other than a few latency issues, it seemed to work pretty well for them.
This setup, though, would have been MUCH preferred.
As for the cost of the second monitor... Most non-pair places buy 2 computers AND 2 monitors... Our stations at work even have 2 monitors per computer, with only 1 developer at it.
I think the cost of the second monitor is a very small price to pay for efficiency.
I'd be willing to check it out for the sake of not rejecting it without cause. However, finding a co-programmer that is a correct match seems to be the biggest challenge.
PS It's good to see that your workers also have decent chairs, and not just gymballs. :-)
I do something similar when I'm pairing, but we just sit on opposite sides of a conference room table. The offset is key so you're not constantly leaning over to see the other person.