Here's my list in no certain order for under 2K...
ArmaLite AR-10 (Where's the Pusher?)
Sig Sauer 716 (Piston driven)
Smith & Wesson M&P 10
Ruger SR-762 (Piston driven)
DPMS
Rock River
Remington SR-25
Fulton Armory FAR-308
CMMG
Availability may play a huge role in which one you choose, some of the wait times are horrific!
If you're going to be hunting with it mostly consider the weight, they can verify from 7.75lbs. to 12.0lbs.
Most of these would need a trigger upgrade, The Rock Rivers & ArmaLites come with decent triggers I hear.
I've read far too many bad things about the CMMG's, I'd stay clear of them.
As far as the 20" barrel goes, I have one and would trade it in a second for an 18"
Some come with ambi features & some don't.
Thanks for your service! & good luck with your purchase <thumbsup>