I sure as heck wouldn't spend all that on one gun.
A good alternative would be a nice custom shop Sig with Damascus grips and a custom Damascus knife to match. Then you would probably have enough for another high end gun or two and a couple cases of ammo.
That's just me.... I don't know what I would do if I had $20k to spend on something like a gun.
Ooooo... Or maybe a nice full auto with a couple cases of ammo to blow through in a couple hours. I still doubt if I would get that though... $20k is a lot of dough to me, I couldn't bring myself to be "frivolous" with it. If you are able to luck dog...