Juzwuz,
Once you get Aspire, you won't need Vcarve Pro any longer. Cut3D, is still needed, valuable. Aspire doesn't carve a 2 sided or 4 sided model, nor does it have another function called 'slicing'.
I've done some 2 sided carving in the past, and that's fun. But, I haven't had a need for 4 sided carving or the slicing function yet.
I think the guys at Vectric got the priorities correct when they developed Aspire. The missing components are not a big priority. For a guy on a budget, I'd recommend buying VcarvePro first and then upgrade to Aspire at a later date.
Over in the Joe 4x4 forum, one guy is building a 4th axis. That would be lots of fun and I might build one someday. If so, the cut3D 4 sided carving would work great with a 4th axis. That's a low priority right now. Even if I had a 4th axis, there are several "wrapper" programs that will transform a flat pattern into a cylindrical design for the 4th axis. Thus my recommendations above to buy VCP first then Aspire.