KC,
if you are going to be doing mostly small game, varmints and up to white tails, then a .223/.556 caliber should be fine (opinons do vary). In Texas I can easily hunt white tails with a proper weight and type of bullet, but shot placement is important.
Brands don't matter a bunch when talking about your lower reciver, as most of them are military spec and manufactured basically the same.
Some brands that have good reputaions are
Smith & Wessson
DMPS
Colt
Rock River Arms
Palmetto State Armory
and the list goes on and on and like I said, opinions vary
I would only say if you are going to hunt and use a scope then search for a true "Optics ready flat top" model
like this rifle
some AR models are "flat top" which means the carry handle is not built into the gun and can be removed leaving a flat picitinny rail for mounting your own optics.
but some of these still have a fixed front site post which can get in the way of your scope and cause distortion.
this is a flat top but with a fixed front site that can't be removed / replaced without an experianced persons help
my recommendation is to get a true flat top with no sites front or rear and you can add a scope or your own iron sites to it as you desire.
I would say to get a decent rifle and a decent scope for it you would be in the $750- up range