That's a tough one because I see GIA stones with those specs from around $22-27k. So let's say the average is $24k. A GIA XXX might get 75-80% of value. Your stone looks great, but you might go more towards the lower end because of vg polish. I would probably ask $20k and leave a little room for negotiating.
You really need to list it so people can email you. They don't necessarily reply to "feeler" threads and especially not with no pricing.