Don't do it! But if you must...
I would add LMT to your list of AR manufacturers, they'll sell you a complete lower and a complete upper separately and then you can pin them together and get around the 11% federal excise tax and put your price point right around the DD rifle.
Seriously though, it's a trap! You're looking to buy an expensive rifle that needs expensive accessories and is specifically designed to blast through expensive ammo quickly. Don't do it. Convinced?