As stated your already set up for what you need.
However, depending you how you feel about stones and grit may have alot more to do with what you want. When you start looking at natural stones, forget about grit size as they are a natural mix of sizes.
It's a hard thing to let go of at times but once you are ready to forget about grit size you will be ready to accept natural hones.
For kitchen knives I have no problem with synthetics, but my razors I find I really want that organic feel to the system. So I'm weining my blades off the sythetics as I replace them. Now I just need 2 more stones and I will have a working system.
You don't need a Japanese natural, unless you really WANT one 