I use a Kawai digital piano at home and found that a sub/sat works best. My set-up wouldn't be appropriate for your needs, but a smallish sub and your pair of (I assume) powered monitors might do the trick.
Good Luck
Marty
PS Try to demo Ivory or Virtual Steinway or similar software. As much as you like the acoustic grand sound that you're getting now, you might be surprised at just how good these hypersampled emulation packages sound.
Good Luck
Marty
PS Try to demo Ivory or Virtual Steinway or similar software. As much as you like the acoustic grand sound that you're getting now, you might be surprised at just how good these hypersampled emulation packages sound.