Sherwin Williams has a beautiful grey called Dovetail. # 6W7018

Yes, I've used them all. Silver fox is the darkest of the three and the most "dead". Meaning it's close to a true gray; not much undertone. With your brown floor and bed, I think this color will get lost.
Revere pewter is a Houzz favorite and recommended frequently. I think that color works best in bright, modern settings with lots of white via trim work or furnishings for contrast.
I like barren plain most from what you have described. It is the lightest and has a cool, steely undertone of gray green.
Hope this helps.

I went crazy trying to find the "perfect gray", Revere Pewter turned lavender on me in the afternoons. I found "Silver Drop" and Silver Birch" both by Behr, very warm, very beautiful.

I am more than going crazy! Barren plain turned very blue on the wall. I just painted Edgecomb Gray and it's not bad either. Along the lines of Revere Pewter, but lighter. I am afraid of Revere Pewter turning too taupey. I can't commit!

I am having the same problem! Someone suggested Stonington Gray from Benjamin Moore. I'm going to grab a sample tomorrow and paint a 3 x 3 sample. It's beyond frustrating to find the perfect gray!

Benjamin Moore's Reverse Pewter will be a better Bet .

Stonington can go green. I have Benjamin Moore Classic Gray in our master and it's warm and stays true to gray. It's very peaceful. For a richer, darker gray you could try Dorian (Sherman W) or Gray's Owl (Benjamin Moore).

I too went through so many grays and the accent colors all had blue undertones which I wanted to stay away from. We finally found a great combo. We did benjamin moore thunder all over our walls and used a darker gray from sherwin williams called Intellectual gray. Definitely get some samples to see how it looks with your lighting. Some other grays to consider are SW amazing gray, dovetail, and gauntlet gray.

http://www.houzz.com/ideabooks/568579/list/Guest-Picks--Find-the-Right-Gray-Paint

I found this link on Houzz and it's really helpful. It lists the colors and tones. There are some gorgeous gray's that don't go green or blue in this post. I hope this helps!