... If anything, buy a Steyr AUG."
Sadly, imported 'assault weapons' are still covered by the 1989 Bush I Ban. The AUG would have to be manufactured here domestically, or assembled according to the '10 Parts' rule to be exempted.
Though it's possible that the AUG could be manufactured in the US under license, the biggest problem is that the AUG's forged aluminum receiver requires sophisticated and wholly-proprietary manufacturing equipment. I recall that it takes something around 200+ individual automated processes to manufacture the receiver alone.
ADI has sold a limited number of AUG receivers in the US since the ban, but they're only authorized by the BATFE for importation as a replacement receiver. The 1989 Bush ban still prohibits these receivers to be constructed as new rifles. Owners of first generation AUGs with the integrated optical sight (made of Swarovski crystal, no less) who wanted the new removeable 'A2' sight rail had to send their original receivers back to Steyr of Austria to be destroyed and replaced with new receivers stamped with the original US serial numbers. The process took over a year and cost well over $1000. I recall something like 50 people total doing this in a one-time 'group buy' offer. Maybe a little more.
Not only that, but AUG parts are as rare as platinum and through the roof on pricing even when you can find them: $250 bolt heads, $500+ for a respring kit (just a little plastic baggie of springs), $700 for the bolt carrier, $350+ for a plastic stock, $800+ for a barrel, etc. etc. etc. There's only one authorized US dealer for Steyr, and they only sell to one or two selected retailers. PJ Investments is the only go-to guy that I know of for AUG parts.
AUGs are priced like Bentley luxury sedans, and are just as rare. They're more of a novelty than anything else.