For myself, at $2500 Canadian I would buy a used Korg Kronos 61 key or 88 key because:
1. it's ridiculously fun to play. the sounds are amazing. the depth of the instrument's capabilities is amazing. there are like 6 or more TYPES of sound engines in it, and tens of thousands of sounds at the flick of a wrist.
2. you could gig with it, not that I currently do.
3. you can load new sounds into it.
4. it's a workstation. it does everything.
5. it's a great master controller.
I think an 88 key might be hard to get used for $2500 canadian, the 88 keys stay around $3000 canadian, but it's close. You might find such a deal if you were sharp.
If I needed 88 key weighted at $2500, and I wanted to go new, I'd get the Yamaha MODX 8. At $2349 it's a beast.
If I wanted a new Korg at $1500-canadian I would go with the Korg Kross 2, and I'd be sad every day that it wasn't a kronos.
None of these would make me a better musician. I already own an acoustic piano and I think that time on my best instrument, spent in a disciplined manner building technique will make me a better musician, not anything I buy.