You also mentioned the "spotlighting" in the showroom. Depending upon what type of lighting it is, you may have problems.
If it's halogen or tungsten, set a custom white balance. There are neat targets available for this purpose (Lastolite EZ Balance are some I use), but even a plain white piece of paper or a "gray card" would be adequate.
If it's fluorescent (or sodium vapor or mercury vapor, which are unlikely), also set a custom white balance, but don't be surprised if some of your shots have color casts and/or exposure issues. These types of lighting cycle on and off 120 times a second, which our eyes don't see but our cameras might. It messes with both the color of light and the level of exposure. Nothing can be done about it (some of the newer Canon models try to deal with it using a Flicker Free technology, but the 6D doesn't). Just take plenty of extra shots and check them as best you can during the shoot, to be sure to get what you need with these types of lights.
You also could use flash, but that will introduce another color of light if it's mixed with the ambient lighting. You either need to filter the flash or filter the ambient light, to try to make them match in color temp.
It might be easier to make long exposures and if you have some issues with shadows, either set up some fill lights using the same bulbs as the ambient lighting uses or use some large white foam core or cardboard to "bounce" some of the ambient light to fill the shadows.
I would certainly use a tripod, too. I'd also use f16 at the smallest (f11 would be better). Use hyperfocal distance to set your point of focus and check things using Depth of Field Preview and Live view, to be sure you have adequate depth of field.
Set an 800 or lower ISO and use a long shutter speed. If your exposure is 1 second or longer you can enable Long Exposure Noise Reduction on the camera, but need to be aware how it works. LENR only works with 1 second or longer exposures, and after your first exposure of the subject, the camera will take a second exposure of the same duration with the shutter closed. It uses this second "blank" exposure to identify the noise in the image, which it then subtracts from the first exposure. If you inadvertently (or deliberately) interrupt the second exposure before it's completed, the camera discards both it and the first shot. (Some people making long exposures with LENR enabled think the camera is going whacky and cancel the second exposure by turning the camera off or pulling the battery, then wonder where their first shot went.)
Yes, selective sharpening such as was mentioned earlier helps minimize the appearance of noise. The 6D is one of the most image noise-free cameras that Canon has ever made, so you might even be able to use higher ISOs. You also can do noise reduction. I do a little in Lightroom, but will also use a Noiseware Photoshop plug-in for especially high ISO shots... It's even possible to do NR in each separate color channel with it, if needed. Do any noise reduction before final sharpening of the image.
Sharpening is best done in steps. Do some in Lightroom, but tread lightly until you have done any cropping and sized the image for it's final use... then finish sharpening with the image magnified so you can watch for any artifacts or other issues that sharpening might cause.
It sounds as if you'll need to do some experimentation... but once you have it worked out, it will be faster to set up and shoot the second and subsequent times.
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & EXPOSUREMANAGER
