The Stronghold is apparently 15K NOT INCLUDING tax and shipping. That exceeded my wildest expectation by 10-12K. So that's my bad. Neither of those roasters look like an upgrade from a FR500 more like a side step.
Honestly just save up more money. You seem like you are on the fence....the picture I am getting is that you would spurge for something like a Bullet if you could get one, but the others are just stepping stones. That's my guess.
It seems like the Quest can last for the long run and is upgradable with lots of advice threads/tutorials here. I would take that over a Kaldi, if I had to choose. The Kakacoo looked like I can build a better one, if I was going to go through the hassle since there are no probes but good wattage.
If you don't care about getting a better taste then don't upgrade, downgrade. Go get a large cast iron pan or better get a cage you can put over a grill. Persoanlly if I was going that way I'd go for this: http://www.auvelcraft.co.jp/coffee/