Cubasis VST 3.7 vs 4.0 vs Cubasis Inwired vs Cubase SX?!?

[Forte]

So I've used Cubasis VST 3.7 - I don't like it.
I downloaded Cubasis InWired and it looked like the same thing - except worst since it's freeware.

So, what's new in 4.0? Looks like they just added some more features, but the concept is the same.

Finally, how do all those compare to Cuabse SX? I hear it's radically different from any Cubase there ever was. I can't even use it though - my system can't handle it. I don't have enough RAM or the right OS.
If SX is that much better, then, I might consider getting it. It seems like Cubase is really high end though and not at all for someone like me.