Good rifle for under $600?

I'm interested in a good rifle for target practice, something that fires cheap ammo, easy to get accessories such as extra mags and optics for, and would be good for when crap hits the fan. I currently own an SKS, a Mossberg 702 and an SKB semi-auto 12 gauge from the 70's. I just want something more modern. If I had my way I'd gladly pay 600 for an ar-15. Even a Remington 700 in .308 would be nice. My local gun store is selling a brand new Romanian AK47 with 2 mags, a case and a cleaning kit for $519. Any suggestions?