This is big, even on the biggest volume exchange that drops the price below $500/BTC. Granted this is slightly priced in so even if it goes that low many people are ready for the drop.
Even if they go through a third party and try to keep it off of the exchanges, there will still need to be an exchange from dollars to bitcoins.
Personally, I will be keeping an eye on that FBI address and when there is movement of coins...that is the time to take advantage.
I hope it happens along with their 140,000 btc , so we can get over this and move on