The piano can be tweaked. I don't care for Yamaha's idea of their default piano. I tend to prefer the Warm Grand and I tweak that until I like it.

The acoustic guitar could be louder on a lot of settings. Just use the balance.

That and finding which touch setting you like the best can make a big difference.

Also, the piano sounds, especially on the PSR's and before Tyros 2 have to be played stereo or they will sound bad. The sounds are phased to make them sound as realistic as they can get.

This was true of PSR's up to the PSR3000. I haven't followed this on the S900 or S910, but my guess is, your piano will sound much better in stereo if you're not using stereo speakers.

Scott