Lobo, There's lots of good VST rompers out there. My suggestion would be to start with what you already have, do some experimentation, and that will likely inform your decision as to what VSTs you may (or may not) be interested in.
Side Note:
As usual, Logo gives me an idea. I'm thinking of a sampling project where I sample attacks and sustained looped portions separately, then combine them in the Prophet X in various ways -- Similar conceptually to the D-50.
Advantages.... smaller file size for the entire sample set. Greater flexibility in combining various attack transients with various sustained loops. Could be a fun little project to work on.