What I do are three things:
1. Selecting the Japanese Grand instead of the German Grand for anything beyond solo play, ballads and jazz trio kind of stuff.
2. Try to get a little bit less mid range and more presence by EQing (still trying to find the best settings)
3. After EQing normally a piano will cut through better, but now you will miss some substance and perceive it as somehow thin. Now you use the "Xaver Fischer trick"

I got this great, really well working tip from this German Keyboarder I know. Meanwhile he has published this tip in a German musician's portal here:
http://www.bonedo.de/artikel/einzelansi ... uehne.html
I include the link, because it contains a sound example
To summarize the essentail point:
- Xaver Fischer mixes a Wurly sound subtly into his EQed Piano sound, to give it back the warmth and bottom it needs, without getting the typical muddy midrange of many pure piano sounds when they are heavily amplified. This way the Piano cuts through without sounding thin.
You will find an example with a Roland piano sound at the bottom of the article:
- first you hear the piano
- then the piano with the mixed in subtle Wurly sound
- then the raw piano again which now really sounds thin in comparison, does it?
It should be possible to find the right mixture of 1./2./3. for your purposes. I would be curious to hear some feedback and pass it on to Xaver.