I don't think you can add the Paramilitary or most ZTs to this group, to be honest. The Paramilitary, like many of Spyderco's knives, are fantastic and more than worth the price you pay, but I think considering them a cut above is untrue. There are many things you can improve on the Paramilitary, for example. With a Sebenza, you're getting the RIL/framelock from the person who's name is in the design, a level of accuracy with parts that is to the extreme, a blade made of steel co-developed by the guy selling the knife, you get a built in secondary market, the history behind the company (just like in the high-end watch world), and you ultimately get a knife that will last you a lifetime. Send it in, for next to nothing you can have it sent back in pristine condition. Now, I don't own any CRKs, but I do see why they're a 'cut above' in a category with mostly custom knives.
ZT offers great value, as well, but they have had a lot of flaws. Messing up the Elmax steel, lock issues with a few models, poor finish and jimping, etc. They do sell a good product and cheaper versions of high-end customs that are fantastic (plus they are really good about warranty work), but they're definitely a notch below the top.
CRK's prestige and the services they offer are two great reasons to buy from them, but that doesn't mean they make the best cutting tools. It's the same reason Rolex and Omega are great...nobody really cares that quartz watches are more accurate than the high end automatic movements they use.
Custom knives are great because the person who designed it is making the one you're using...and that's really nice especially when it's someone well known. I guess that is part of why CRK is similar to them, too. Owning a piece of history, in a way. Just my .02