I'm a big believer in using what you have and I'm sure your norton and super stones will do the job just fine. I'm guessing you made an error and you have a 220-1000 combo stone instead of a 220-100.
I think your technique will have more to do with your results than shelling out more money for more stones. So I encourage you to use the ones you have now and as you wear them out you can contemplate trying some different ones.
You do need a flattening method and I would recommend the DMT 140 grit diamon plate: http://www.chefknivestogo.com/dmtextracoarse.html
This plate will take care of all your flattening needs.
I would also recommend you add a strop or two and maybe some diamond spray if you're sharpening razors. You may have this stuff and didn't mention it.