If you can find something similar at a local mom and pop shop you'll prolly get it for the same price but without tax. That's to say you'll get it roughly $200 bucks cheaper and with tax you'll break even with the GC price.
I'd say play your cards for awhile before springing on 1 guitar, you know? Spending months finding that perfect guitar that just comes alive in your hands is well worth the wait. Plus $3100 (that's with tax) is a lot of money, and because it's the GC you're not the first one to play it and put it back on the wall. I'd say find the smallest (while still significant) things to bump the price down. That's scratches to the finish, any buckle rash, pick scratches, fret wear, random bump marks on the ever so soft nitro...that kind of thing. Get what you're paying for!
Not exactly any word on Supremes in general...but Gibson has their good and bad days as far as quality control, so if you found a good one then kudos!
And if you decide to get it, take some pictures!
"Music is the only thing that you can share with a million million people and you don't lose, you gain. It helps you to get energy and to live long, because when your soul is very happy then you don't want to die." - Ali Akbar Khan