keystep pro can pretty easily do what you want but if your kurzweil is full size I don’t know if I can recommend it. I went from similar situation, older full size controller but very limited midi capability to keystep pro and for a few reasons I’m not real thrilled with it. I’ve always liked keyboards and synths with mini keys but I guess I was more used to full sized keys than I realized and it’s not that comfortable for me on the keystep pro. Also, I find that the range of velocity sensitivity on keystep pro goes from bad to worse, none of the 3 curves are to my liking. All are much too sensitive, I have to strike the keys much harder than I’m accustomed to playing in order to get full velocity out of live playing and it’s distracting. Also the amount of in’s and outs is really good but the connectivity with other gear is not always there like I had expected out of something that is supposed to be the ultimate controller hub (from how it was sold and advertised to be). The sequencer though, especially the drum track, is really good and intuitive, it’s easy to use with good results and there are a lot of nice features, the device is well made but as a keyboard midi controller which is exactly what I need / want it to be, I’m not super thrilled with it. Especially for the price.
I think you’re headed in the right direction, if you’re comfortable with your current controller and just want more versatility in the routing probably worth waiting to find a deal on one of these hardware go-betweens even if it’s used. Midi gear that doesn’t rely on buttons and keybeds, i.e. not controllers, don’t really seem to go “bad” unless it’s abused, it all sees such low voltage that they seem to last through a couple owners.
Just my 2 cents. Have a long sit down with keystep pro before you commit to it as an electric piano type substitute.