As best I can tell, Cubase 4 (not Cubase Systen 4, which is just hardware bundled with Cubase SL3) is the next version of Cubase SX 3. Apparently, they dropped the SX in the latest version---probably because of the obvious pronunciation. They just announced it, and it starts shipping in a little over a week.
I still have a copy of Cubase SX 1.0 PC/Mac, complete with dongle. It hasn't ever been registered/installed. I'd like to get out of it what I paid. If only I could remember what that was.
I think about $200. If you decide you like SX, you can upgrade to Cubase 4 from SX 1.0 for $249.
So basically, buying that and buying the upgrade would be more than half off
the Cubase 4 retail ($450 instead of $999). I'm not sure what the mail order houses are going to charge for Cubase 4.0 yet, but I'd be surprised if they sold it for less than half retail (education pricing notwithstanding).
So $200 shipped (ground) to the continental U.S., else $195 + actual shipping. PM me if you want it, and I'll send you PayPal info.