You've been given some very good advice and I can only add my very limited experience.
I'm currently on my second AR. First was a Bushmaster bought during the '94 ban. It has since been sold for financial reasons. It was a good rifle and bought used. My second and newest rifle is from a stripped Stag lower and a Del-ton upper. A friend helped me build it out. So far I have nothing negative to say about the upper. It is a base model upper and I bought it for about $375. So yes the is a budget rifle. Accuracy has been fine for me and function has been 100%.
If your budget can handle it then by all means look into others but don't be afraid of some of the smaller budget manufacturers either.
Now, in my opinion I prefer to buy a basic rifle and build it up myself choosing the parts such as handguards, stocks, grips, and optics. I know you can buy a built rifle and probably with all your desired features but I find it more fun and a way for an AR noob like myself to learn more about the rifle.
Whichever direction you choose enjoy and have fun.