I have an SX, but in the process of switching over to MCX8000 (I can’t use my old software, so there is a bit of a migration issue still). The SX(2) is nice as is the RX. The latter one obviously is RekordBox “locked”, where the SX2 gives you the option of using just about any other DJ software. So if you are not sure if RekordBox is THE software for you (as in most closely supporting your -intended- workflow), the SX2 will give you more flexibility. The MCX8000 is great controller, adds screens and a (backup) option of DJ-ing without laptop. We are waiting for the new software for it, in which case the stand-alone (no laptop) option will become good enough to use that full time to.
You WILL see massive increase of options over a CDJ set-up imho.