Remember that the DGX650 which has the exact same piano as the P-105 and sells for $599 without the stand and has 10 drum beats, no arranger at all and only has about 20 sounds is only $200.00 more! and has styles, hundreds of sounds, USB audio recording, a beautiful wooden stand, 6 track recording, lyrics and score on screen, etc. etc.
The DGX will not sound thin when you output it into a nice sound system. That is what I'm doing at my store and I don't think the internal speakers sound think at all, just not as good as bigger and more powerful speakers.