The biggest problem with no-name Chinese bikes aside from build quality (welds, low quality hardware, metallurgy), is support and service. When, not if, the company/distributor folds, where do you get parts and service?
So many fly by night operations and used car dealers decide to sell these low cost Chinese bikes, CCW's, Sym, etc and the like, and in a year they either close down or stop selling them, and you're on your own.
For $6000, I wouldn't think twice about buying a used KLR, DR, heck for $6000 you can get a used WR250 or even a brand new XT250... the choices are endless, really, and you'll get a much better bike.