While the CRKT's I have a great knives for the money (the best super-cheap knives available, IMO), they are no Spydies.
The Spyderco's are tighter, use better steel, almost always have better ergonomics and come with a customer service/refurb policy that is hard to believe. They have better utilitarian designs in the line, and there a few Spydie designs that enjoy rightfully deserved fame as some of the best value tools available for their uses: like the Calypso Jr, Rescue, Delica and Military - for just a few. Some of them are real works of art. I've sent a Spydie back to the factory that I had literally just abused the tip right off of, and they sent it back completely re-furbished with a letter explaining what they had done...for free.
That said, if you have a bunch of Spydie's and are looking for some variety - CRKT has some cool stuff. I like their super-cheap stuff the best. It's always great to get a knife you find yourself using regularly for less than $20. I use their Stiff KISS as a dive knife, have used the PECK for a money clip and occasionally carry the Kasper folder if I want to backup my Benchmade 710 for some reason...like extreme paranoia or something.
The M-16's are cool, but bulky and hard to pocket carry discreetly with the clip mounted so far down that the knife rides up out of the pocket a bit.
- Gabe