The goal is to have a floor that looks nice with minimal budget and minimal time (hard to close for more than a weekend). Not married to the idea of any one flooring over another.
Only addressing the floor in the showroom. The floor in the back is not coated so we don't need to worry with it yet.
As far as look, I personally like epoxy BUT we all know it's expensive and time consuming to lay down epoxy. So I am open to anything.
A floor that looks nice, that doesn't cost much. Such a rare request.
I coat of floor paint is the quickest and cheapest, and it looks it. The next step up is VCT, but that means proper prep, and without knowing what that coating is, I would have a tough time guessing.
Here would be my recommendation. It could be done in a weekend, but it's going to be an intensive weekend, and some of the steps are on the low to medium skill level. It's on the low-medium budget scale.
I would recommend an LVT or LVP product. I like Armstrong's Natural Creations. It's very durable. It's fairly common in a retail environment.
http://www.armstrong.com/commflooringna/products/lvt
For prep, I would recommend taking a 4" floor scraper and getting up all loos material. Remember, your floor is only as good as its weakest bond-line. From there I would recommend Ardex P-51 Primer,
http://www.ardex.com/cms%5CAssets%5CProducts%5CDocumentation%5Card-p51-tech-us-e.pdf, and then a double skim coat of Ardex Feather Finish,
http://www.ardex.com/cms%5CAssets%5CProducts%5CDocumentation%5Card-sdf-tech-us-e.pdf. Sand a smooth finish, and then follow the instructions for installation of the flooring material. I would recommend a good 6" rubber base to finish it off.
Another option, but I am not a fan of it, is, a commercial grade laminate floor. It's a floating floor, so the bond to the slab is not an issue. But... be sure to use a pad with a good vapor barrier. Laminates do not like vapor emissions.