If you're thinking about getting a new controller ~and~ a sound module, consider a Yamaha CS1X or AN1X. Both have a good rep as reliable, versatile controllers as well as a good range of sounds. I think they both have follow on models with a 2 where the 1 is.

Best place for gear reviews is sonicstate.com/synth or /studio

There are quite a few keyboards and modules from the 90s that have a "PC/Mac" input - which is (ta-daaa!) an 8 pin miniDIN serial port. One of them and you don't even need the Mac MIDI interface, just a modem/printer cable. Some of them will even pass signals back and forth between that port and their own MIDI ports, acting as an interface to other gear.