C5 is the first with render-time micro displacement built-in. As people are keen to open old files, Eric has updated it to be backward compatible. I think the new displacement is a giant step forward. I don't think there is any need to buy Anything Grooves when you have C5. The new function in C5 does, what AGrooves provided before, but faster and smoother (and with 16-bit grayscale compatibility, which gives you much more than the old 256 shades of gray to define your heights).