Get yourself a set of Venev diamond stones. They are not diamond plated stones like the generic diamond stones that you get with TSPROF systems, the Venev stones are actually diamond bonded stones (diamond powder mixed with a resin bond) so they perform like water stones (most Japanese synthetic stones are Aluminum oxide in various bonds). Venev stones will cut any steel you throw at them, and you will get superb edges from them.
I have sets of Naniwa Chosera, Naniwa Superstones, various Shapton stones, and many, many others but I still prefer my Venev stones for their versatility and performance.
When it comes to their grit rating, don't be fooled into thinking the finest 1200 grit Venev is "coarse", it's actually a different grit rating (Fepa-F) compared to the Japanese stones (JIS). The Venev 1200 is more equal to around a Japanese 5000-6000 grit stone.
The dual sided 6" Venev stones are unbeatable value for money.
Your best place to find Venev stones (and just about any other stones you may ever need), is Gritomatic. They sell dual sided Venev "Centaur" and Venev "Ursa" stones for a really good price.