The WASR's have improved in quality by quite a bit to being what many consider a good AKM variant. It comes with a Cold Hammer Forged Chrome-lined barrel which is a plus if you decide to shoot corrosive. JGsales has WASRs right now for $500 that comes with a 75 round drum.
NPAPs have a great reputation for fit and finish, but as previously mentioned you have to find Yugo specific furniture. Also the barrel is not Chrome-lined. There are debates out the yin-yang as to how important this is. Personally I'd rather have Chrome-lined.
The early C39v1s did have non-chrome-lined barrels but most do by now. I think the v2's have started coming with nitrided barrels which many herald as better than chrome-lining. Time will tell. But look at the serial number on the v1's the chromed has an extra letter in the serial number, I think it might be a C, but be sure to look that up as my memory on the letter might be wrong.
Some considerations that you didn't mention, Century just released the RAS 47 which is a lot like the C39 but with a stamped receiver so it will be lighter. It also comes with a side rail mount whereas the C39 will need to have one mounted unless you want to put the optics elsewhere, like putting a railed gas tube on the front.
Also Palmetto State Armory is going to be making an AKM here in the next month or two so if you have patience that would be an option. I haven't heard solid specs on it yet, but the price tag is going to be in the neighborhood of $600. I am pretty sure that it will have either a chromed or nitrided barrel, but that is subject to new info.