Which speaker has the biggest sound stage?

Good Post Larry. Perfect example of a self appointed expert, that likes to hear them self's talk.

To answer the OPs question, yes fairly all larger panel speakers have this huge soundstage. An eception might be the Magnepan MMG for its dinky size, it certainly is not capable of the vastness of the bigger panel speakers.

Besides Magnepan you've got the aforementioned Analysis, Sound Lab and Kings Audio (reviewed). Quad makes a couple of bass shy full range ESLs. Then you have hybrids which really are all over the place in terms of how much panel element is built into them. VMPS has quite a bit, but Legacy Audio uses only one planar element in the Whisper and Helix (reviewed). Eminent Technology has a very similar concept to Magnepan, but is a hybrid with a sealed 8" bass driver per channel (reviewed). The Janzen is also thinner ESL hybrid. Martin Logan is a hybrid with a curved ESL panel, which may/may not require subs added to satisfy.

One thing to keep in mind is the width of the soundstage, as people have distinct preferences in this regard. Some don't mind a narrow sweet spot while others find it intolerable. You will definitely have more lateral extension to it with the wider panels in general.

As to the largest, if you want a planar sound the Magnepan 20.1 is among the biggest, and if you prefer an ESL sound the King is quite competent. The biggest and having among the best sound is the Sound Lab. Pay careful attention to the bass response especially if coming from a larger/deeper bass full range speaker, as you may end up feeling the bass is insufficient with some of these brands.

Texas,
You and Elizabeth should huddle together, start selling glue for Maggies.
What I said, to repeat, is that, in my 15 years of selling them, AND servicing older pairs, that it happened, "NOT ONCE".
I didn't say it couldn't happen. Elizabeth's post made it sound as if it's a common occurance, one she felt the need to publish a cautionary warning for...IME that didn't happen.

PS. Don't back stock a LOT of glue...

Good listening,
Larry

MBL 101 is the runaway champ IME. Ohms do a great job, too.

Sorry, misread the OP. Please disregard the above.