I'm kind of foolhardy I suppose, but I find the notion that you "need" to learn another synthetic before getting another finisher rather silly. To be perfectly frank, you "should" learn to get really good shaves off your norton combo. Then, after reading people's opinions that you respect, make a decision on what you want and learn it, be it synthetic or natural. Both types of hones have their merits, and ultimately the decision is yours.

I can tell you that my best edges from both types have been equally excellent, but I find naturals to have much more appeal to me. However, it's all moot. If you know how to get an edge from your current setup that shaves really well, this decision will be more about the experience than the results, in my humble opinion.

Good luck