The CG Jackson/X-Treme is pretty incredible. I recently put one on my tube gun and am very impressed. Well worth the money. One potential drawback is that you can't adjust it down as low as some others. In my case, I wanted about two pounds total, so it's great, but if you're looking for a pull in ounces, look elsewhere. Because it is so clean and precise, it feels lighter than it really is.
I would also say that customer service was not great, PM me for details if you want. Read German Salazar's articles on the trigger for more info and reviews, he seems to be a big fan as well.
I would love to try the Tubb, and have heard good things about it. If it had been available a year ago, I might have tried it instead.
My understanding of the Huber is that it's not really a true two stage. As I understand it, once you take up the first stage, you have to reset the bolt to reset the trigger. In other words, once you take the slack out of the first stage, you have a single stage trigger until you reset it by working the bolt.
One other to look at is a Bix and Andy. They're a little higher, but they're supposed to be flat out awesome.
ETA: as to price, you're shopping in the deep end of the pool. These days, a quality two stage trigger for a bolt gun is a very specific and low volume item. All of the manufacturers you mention produce extremely high quality products essentially one at a time.
