general AK pros/cons:
pros:
+invincible platform
+unmatched reliability
+simplicity and ease of maintenance
+power
+cheap, steel, life-lasting mags
+is usually inexpensive
cons:
-ergonomics of a tree branch
-very crude sights
-accuracy ranges from about 2.5-5 inch MoA
-more recoil
your Bulgarian Arsenals are your best, but they run for the price of a top-shelf AR (~$1200-1500). IMO, not worth it. The AR is a better platform, and for the same price that is what I would choose.
Your next bet is the Saiga. they are Russian hunting carbines that get 're-converted' back to their original evil forms. Buying a Saiga and converting it yourself will set you back about 600-650 bucks for the gun and conversion parts, assuming you have the necessary common tools. You can also opt to buy them already converted from Arsenal or some other places for about $650-800.
After that comes your polytech/norinco models and your Yugoslavian models. Good accuracy and quality - especially in the Yugos. The yugos don't have chrome-lined bores, which gives them better accuracy; make sure you clean the barrel well, though. Both are also no longer being found state-side because of the Norinco ban and the drying up of Yugo kits, so for collectors' sake those two are good grabs (about $700 a piece). Then there are the SSR-85 Bulgarians. These are not real arsenal AKs, and there have been reports of problems with them. Same goes for other AKs in the same ballpark, like Lancaster and Vectors; basically WASR-quality AKs with a nice outer finish and internal parts of unknown provenance.
Then you have your WASRs. These run from $500-600 now. They used to be dirt cheap, but because of the panic...yea. You may be able to score them for around $400 if you look for it. These are your bottom-of-the-barrel in terms of quality, but they work just as well, and the accuracy is not much worse than even your better makes.
Personally, the Saiga conversion is the best for the buck. Better-than-average accuracy and great quality for about half the price of an Arsenal Bulgarian. Just remember that the accuracy difference between your Arsenal and your WASR is not much to gawk at or justify an extra 800 bucks; usually the difference is mostly brand-name and cosmetic finish and add-ons that just make the gun look cooler for the most part (the only exception is the presence of a muzzle break, since these DO help out noticeably)
(PS - I have a converted Saiga.)