If you limit yourself to touchups only the Naniwa 12K and whichever Naniwas you would use for a pyramid (8K and 5K or maybe 3K?) should be more than adequate. Include a pasted/sprayed strop and you should be in great shape.
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If you have a leather strop, and you just want to maintain pre-sharpened razors, then just get a barber hone.
The C12k will probably be the same thing if you choose to go that route. I have yet to pick up a barber hone, and if I really just need to touch up my razor and the leather, or CrOx isn't working, the C12k will do the job.
YES, the C12k stone is slow, but if you can saw off a piece to use as a slurry stone (or just buy a slurry stone for it from the classifieds, I think it was zib, but he may not have anymore) then the slurry will seriously cut down on the amount of passes you need to do on it.
Personally, I'll go with the C12k, but I may eventually get a barber hone to try out. Just my 2cents...