Timo1,
If possible try it out with an external sound system or headphones. I think it would sound great with a 50 - 100 watts 2.1 sound system. The accoustic piano on the Roland has more volume then the Yamaha's. Where as the Yamaha's need to be cranked to half-way, the Roland would be at a quarter for the same volume level. I find the EXR-7 is brighter then Yamaha pianos.
Painkiller,
Did you ever try your EXR-7 with an external soundsystem.