I tried them all over the last 10 years. Here is my unequivocal opinion :
If you cannot afford a National or a Dobro, the best, by far and with very little competition in the $500-750 US range, is the Beard Goldtone.
Johnsons vary among themselves from average/rarely good to disaster. I owned a pretty good one, but they just don't compare to National or Beard Goldtone.

The previous writer is correct that almost all the others are made by Samick and almost all suck horribly. If you go to the store and try dozens, you will always find one that's "reasonably" OK, but they are rarely "good" and certainly don't hold the value and all are a bad investment.

I now own a National El Trovador and a Goldtone Weissenborn. The Goldtone is as good as any Weissenborn out there--no matter what the price.Solid mahogany and nicely made, sweet sounding.

Beard Goldtones, of any variety, are really wonderful, well-made and great sounding. They come in round neck and square neck. I would buy any of the Beard Goldtones without hesitation.Beard himself assured that the Asian manufacture is spot on to his excellent standard. I also encourage people not ever to estimate the craftsmanship of Asian instrument makers. The problem is in the quality of the company--and Samick just does not understand the instruments they are copying.