Since it seems you like diamonds, I'd say just get the DMT diasharp benchstones, full size 8"x3". The full range would be EEC, EC, C, F, EF, EEF. If your knives don't typically recieve heavy damage or you don't do a lot of reprofiling, then you can skip the EEC and EC. In a pinch you could get heavy work done with coarse sandpaper on a flat hard backing. You could probably also skip one of the fine stones if you are not going for a perfect mirror polish. So maybe a 3 stone starter set of C - F - EF then strop. Then you can fill it out later with the EC/EEC and the EEF.
The diamond stones are nice because they will easily handle all types of steel, even ceramic knives, and they stay flat.
You could also go the waterstone route. Waterstones are nicer to use (hard to explain, but there's a very nice feedback you get), but more expensive, messy, and require more maintenance than the diamonds. Most of them require soaking in water for several minutes prior to use, which cuts down on the convenience factor somewhat. There are a lot of times I want to do a little touch up on a knife, but don't want to bother with dragging out the water tub and soaking and then putting them out to dry later. With the diamond stones you can use them dry or just splash/mist a little soapy water on them and you're good to go.
However, water stones will sharpen very quickly and seem to give a better polish for a given grit than sandpaper or diamonds. If you are really into the "Zen" of sharpening then I doubt other stones facilitate this more than waterstones.
Also, I have heard good things about the Spyderco UF ceramic stone, and I'm seriously considering getting one as a finishing/touch up stone.