I am under the impression that 154cm is a relatively forgiving metal that can easily be sharpened with conventional sharpeners - water/oil stones, carbundium, etc. I've had no issues doing such.
It is some of the newer steels like S30V and older big carbide metals (D2, maybe)that going to diamond really makes the difference.
Personally, if I had to do it all again, I'd invest in some good diamond bench stones (DMT) and some diamond paste (for stropping) from the get go. That way I wouldn't have gone through so much $$$ in my sharpening journey.
As a starter for little $$$, I still recommend the standby SHARPMAKER, if for no other reason in that everyone talks about them so it is good to have some experience with it. Maybe through in a DUCKFOOT for faster rebevelling. If you look around, a Grant ($50) should bring the two home with a small bottle of Militec as company.
The SHARPMAKER is a good sharpener, BTW.