Hi Graham
The comparison was actually 2 pronged.
1. Stage performances using the same Amp/Speaker system. (Live environment)
2. Headphones
I also had a listen to the PA 800 inbuilt speakers, and for the size they were excellent. (Much better then the Roland E80 for example)
The Yamaha Tyros 2 speakers as I have mentioned before are not worth putting on a wind up gramophone, they are awful, and make the Tyros 2 sound like its being played from inside a padded cell. (Yuk)
Hope this helps

Bill