You first statement "I recently purchased my first good pocket knife, a large Sebenza 21, and I don't think I am going to stop anytime soon." makes me want to agree with the others saying to go ahead and get a bigger kit now. I started collecting while I was in the military, but that was buying from the BX, etc., I had NO CLUE about the vast world of knives to be had. You have just purchased one of the icon blades, and it wasn't cheap, and you already acknowledge that you are addicted. If you are also interested in fixed knives (other than kitchen knives, I mean hunting knives, tacticals, utility, etc.), then your world of options just doubled, there are some real beauties out there!
Since you are already an admitted new blade crack head, if you can swing it, I would go with the PPII if I were you, otherwise the PPI with the upgraded arms. Mainly because it comes with the more flexible angle system, degree system, and the riser to allow for shallower angles, along with the ceramics, finer micron diamond strops, the digital angle item, etc. Relatively speaking, the cost is about 1.5 times that of the Sebenza, but if you continue to collect knives of that caliber then it will be a relatively small investment relatively speaking with which you can maintain your collection if you continue to collect in that price range or higher, then you will have the best system money can by to maintain or improve your collections aesthetics, not to mention keep those kitchen knives sharp!
And if you happen to know others that need knife sharpening, once you are practiced, you will have enough of the stones and strops to be able to handle quite a few requests... making some of that $ back (that is my plan anyway ).
P.S. I mean crack head in the nicest way possible and no offense intended to actual crack heads , aka blade collecting and/or using addict, is there a better more politically correct term for that? I am one myself, I am drawn to things that are well engineered and combine that with the beauty of materials and the science of steels that appeals to my geek side, I cannot be helped . Ironically, purchasing my Sebenza was what really screwed me, just slowly opening and closing it, admiring the perfection in action and construction, trying to find a flaw and not being able to... hooked .