I’d give the GAS (gear acquisition syndrome!) a break for a while. 😂

There is plenty to work on with just your BK9 and DAW, and a long way to go before you max out their potential, anything extra is just going to distract.

If you’re contemplating adding something to your rig, for starters, if you are either singing or recording real instruments to add to your songs, you want a decent microphone. And if you want to add another keyboard or module, I’d recommend another brand. Another Roland will sound pretty close to what you have, but EVERYTHING in a Yamaha or Korg will sound totally different, which gives you more options.

GAS rarely solves anything! Mastering what you have is far cheaper and way more effective!