If synthetic stones are your choice. You want repeatable exceptional edges, then equip yourself with a progression you won't need to change for the foreseeable future try this: Naniwa Chosera 1k, the Naniwa superstones 3k, 5k, 8k, then jump straight to a Suehiro Gokumyo 20k. It does work, and of course you must have a quality 8k edge before going any further. Some wish to go to a 12k Naniwa before the 20k, but INMHO you don't need the 12k and the20k. This progression works. If for some reason you feel you must have a12k then so be it, but I don't think it's a good spend.