Kaj,
I got a DMT Aligner and a Gatco system, and all I know is that DMT makes better diamond stones. You can adjust the angle in 7 steps. BUT, the plastic clamp sucks. In my case, the screw at times untighten itself, making it unsecure. Also the clamp will only stick about 2 mm on your blade's spine. Right now, the only way I'll use my DMT Aligner is by using a Lansky clamp.
Now about the Apex. My brother has one and IMO it's one of the best sharpening system out there now. AFAIK, Ben Dale doesn't supply diamond stones for his systems, but you can ask him for extra supplies to make your own Apex diamond system.
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Reynaert
Fayetteville, AR