I’ve also had the VMS4 almost 2 years and there are not many controllers out there that can be considered an upgrate future/price whise. Over the 2 years there are only 4 that I’ve seen as an upgrade from VMS4. They are VMS4.1 (only for the better sound) Numark 4TRAK,Vestax VCI400 and Pioneer DDJ SX (It’s what I’m getting) but these all cost quite a bit more then the VMS4. You could also add some controller insted of upgrating. So I’d say as Terry “What is missing from the VMS4” can it be added with an extra controller. Some of the comming Beheringer CMD controllers might be what you need to get that extra controlls.