Speaker set up for more than 1 person

A lot of this depends on the speaker tech. The KEF Blade for example has a huge, sweet spot. I think coincident drivers tend to have a slightly bigger sweet spot, with the Blade being very special in this regard.

I enjoyed the Magnepan LRS and Mini for not being so restrictive on the seating. I use the Mini in my office.

What you are asking for is impossible. All your friends will never get good soundstage and centered imagine. The stereo format was not designed for this. That’s its main weakness. Look into multichannel music systems using more than a pair of speakers for that. It goes without saying that the music must be encoded in that particular format. With stereo, the best you can achieve is for two people sitting close together to get decent imaging. The speakers dispersion pattern will dictate how far you can go. DSP systems like BACCH might help. However, the main listening position (MLP) will always be the sweet spot. 

Its completely normal for the sweet spot to move with the listener in a properly set up speaker arrangement. Anything you do to accommodate additional listeners occupying the sofa will compromise the sweet spot for whoever is sitting there. Why not take turns listening when the fellas are over to play hi fi. Personally, I wouldn't want to have to smell them when you're all sitting elbow to elbow!

My main listening room has a single recliner in the sweet spot.  If my girlfriend is over I'll let her sit there and I throw a bean bag chair next to her.    

I agree with Spenav. What you're trying to achieve is fundamentally not possible. A true center image is only possible by one listener sitting precisely between the speakers. Set your speakers and chair up just for one person and then don't tinker with them!