I had a small exhibition with B&W prints up to A3+ (the largest my Canon 9500 Mark II can print). All images were shot with the X100. The visitors, amongst which many photographers, specifically complimented me on the quality and sharpness of the prints.
These were from RAW files though. The Xe-1 raw files were not to my liking because of the "painting effect". It seems to improve though. I sold the camera, but still use the X100. I printed a JPG from the XE-1 on A3+ though, seemed good enough, lacking some depth I thought, but that was just one image and mainly caused by my editing (just a test after all).
I have been testing different camera's prints on my Canon Printer. For me, decently shot RAW files starting at 12MP, up to 800 ISO, from recent cameras, are no problem for A3+.
And I hold the print in front of my face, and have perfect vision.
Smaller files, or higher ISO's, could work too, depending on individual situations. But I have set my minimum requirement at 12MP for all my work.
One interesting thing that I noticed, was that while printing I would notice more grain in higher ISOs (including 800), but when at the exhibition, I completely forgot about that, and didn't notice any difference between the mages ranging from 200 to 800 ISO (probably even 1600, simply didn't remember or care).
If you are okay with the RAW files, then you will also be okay with very large prints, beyond A3, I think.