Another option would be for you to buy higher end parts a few at a time and build up your own breed of AR.
Building up your own gun with the parts you think are cool is a pretty fun way to get into the AR game inexpensively.
Here's a forum that has just about anything you want to know about home brew AR's.
I would also suggest checking the www.utahgunexchange.com and www.armslist.com classifieds for pieces and parts. Guys are always swapping in and out pieces parts to suit some new fangled desire
I've attached a pic of my latest AR308 build I'm working on. Next will be an identical version in 6.5 Creedmore (necked down 308).
Just understand, this game is a can of worms to say the least