I have a Sanyo 5600, and love it.
It is loud and easy to use.
It gets dropped and abused and just keeps on going. Great looking screen and battery life is good.
Can not really comment on the 8200 or 8300.
Sanyo 8300 is better than the 8200, video, better UI, and better keys by far.
Of course I am talking from a sales point of view, and I seem to receive less Sanyo 8300's for repair currently, compared to the 8200 (before it was EOL).
Sanyo 5600, is better again, music, good loud ring (loud true tones too), good UI, and mp3 player, but if you can afford it the Sanyo 9000 is just that little bit better again, EVDO makes a big difference to watching video clips etc.
Cheers and good luck!