my first pair of mics was a set of AKG 391's. I paid $450 for the pair, so they can definitely be had in your price range.
Additionally, I would keep your eyes open for a pair of used AKG 460's. I think the 460's sound better than the 300's, and I think I've seen used pairs (with one set of caps) go for right around $600 (or maybe less?).