Another nod for Restoration Hardware. I just installed mine last night along with RH sconces and I couldn't be happier. Excellent quality, very sturdy construction. A warning about your plan. I considered the same idea for the framelass glass medicine cabinet in my other bathroom. It's nearly flush with the wall sticking out only the thickness of the door. If you slap a frame around the door, it can't open because the hinge is flush with the wall and the frame on that side would hit the wall. Part or all of your frame would have to be mounted to the wall to make this work. It can be done, but takes some planning and likely some fine woodworking skills. Joe

Can you mock up what the mirror and vanity will look like - use some painters tape to indicate where in the room the vanity will end and then outline the various choices of mirror/mirror cabinets. You might be surprised at how some work better than others. With the Kohler Verdera 101cm (40") by 76cm (30") medicine cabinet, it doesn't matter if it's 7" shorter than the sink - what matters is if you are using the sink to wash up, and you look up - are you able to see yourself properly in the mirror? IOW, is it functional.

How much space do you have between the cabinet and the wall? Did you look at Mirror Mates? I don't know how it works with multiple doors but you could take a look at this. I googled like crazy and didn't find much. I like the frame that Kohler has for the Verdera cabinet - nice simple lines. I was thinking of going that way but this only works with recessed mounted ones and ours will be surface mounted and none of the stains worked. I have been on the hunt for a framed med cabinet and it hasn't been easy finding one that meets my requirements. The back up plan is the tri-view verdera and the contractor making a frame like they have. I am looking at some cabinets this weekend and am hopeful that I will find one that works without having to go with the back up plan. I would just rather see the finished look and save that added time. What brand do you have? That compnay might have something.

For size, you can also get customized sizing where cabinets can be ganged together. For example, two 12 inch cabinets ganged together or two 15" ganged together would work where you can add lighting as an option and have interchangeable left or right open doors. It gives you alot of storage over your vanity without looking too wide. And if you want to spend the extra cost, you can have them recessed mounted as well. This will make them look flush with wall and less bulky over any sized vanity. And some of these mirrored medicine cabinets have integrated LED lighting, which can also offer a nightlight with dinner function. So, you will not only have lighting from your main bathroom, but an additional light source. I hope this helps