My first AR was a Del-Ton. Still have it, and it's had a lot of rounds through it. I've built a handful of them using Del-Ton stripped uppers and lowers. They make a pretty good product. Even if you wanted to go with a basic model, it would be easy to upgrade it later.

Just to be fair, DPMS is another good brand. They make a model called the Sportical. I think you can still find them on sale for $499. They're nothin fancy, but throw a nice trigger in one, and they'll shoot with the best of 'em.