The way I see you going at this moment, you don't appear to have a clear picture of what it is that you want/need. I'm not referring to audio components,,,, I'm referring to the tasks you wish to accomplish. Small monitors are probably fine for listening to music,,,,, using your synth as a dedicated instrument however, might present a very different set of issues.
The VERY FIRST thing I'd do if I were in your shoes, is get myself to a pro-audio store, and have a talk with a "competent" sales-person/dealer. Explain precisely what it is you wish to accomplish. Bring your synth with you. Listen to as many systems as you feel necessary,,, even if you have no intention to buy at that moment. Just assess the impact of those various choices/options vs how well the various systems meet those specific needs. Ask if you can try this gear at home for a day or two. You might also be able to rent that gear by the day/week. etc.
Don't be too reliant on 'specs"; remember, a speaker manufacturer may be using a little creative marketing to achieve those "great looking paper-specs",,,, that's what "sells" gear. Just trust your ears, and consider warranty and after-sale parts and service availability.... and their return policy. Make a check-list before going to the store,,,, listing everything you want to consider when auditioning that gear.This is something you're going to have-to do.(listening in person) At the end of the day, even if you decide you don't need "new gear", and you decide to repair what you do have,,,, you'll at least know what the possibilities were, and there's "no-charge" for that.