I’m pretty familiar with the Olympica 3 - they were on my short list. Though they’re wonderful speakers, I didn’t get them because they weren’t a good fit for my room. I haven’t heard the Nova 2, but it seems reasonable to assume they are voiced similarly to the previous model line though perhaps a bit less warm.
I don’t think you can make a mistake in general as they’ll both be good speakers. But, you can make a better decision by considering the following:
1) size of your room
2) where you’ll place the speakers in the room and the space you’re able to give them with that placing
3) what you listen to and how you listen
The OIIIs are very good speakers, but voiced to be warm overall. Placing them too close to a wall or particularly in corners will exacerbate this characteristic due to the output from the rear ports. This can be somewhat addressed by having the ports face toward each other or away from each other depending on which speaker you put left and right. If you’re near sidewalls, you probably wouldn’t want the ports facing outside unless you really like a lot of bass. I’ve heard them set up at dealers this way and thought they were doing a disservice to the brand and model. Regardless of port direction, I am guessing that the OIIIs will have a more lower range power than your Grand Pianos. If you have space to bring them out from the wall and sidewalls, then this isn’t really a concern.
Lastly, if your room is smallish, then I’d worry about overloading it and would favor the Nova IIs.
Good luck and let us know what you decide to do.
Best,