I have the Pio 656 after trying the Toshiba 220. The picture and sound on the 656 seem very good to me but I had no chance to test the 2 players side-by-side. Uncle Eric and others seem to like the 656 too. I don't know if the 220 shares components with the 520, but here are my commments between the 2:
Pio 656 pros: It works on all disks I've tried (mostly R2), good setup menus, quiet enough, great output options
Pio 656 cons: No news on progressive capabilities/ upgrade potential
Toshiba 220 pros: Zoom modes work during playback, so you can choose to get rid of the top/ bottom black bars on wider-than-widescreen DVDs, good picture and sound
Toshiba 220 cons: It freezes at layer changes on some disks (e.g. Pulp Fiction, Dinosaur)
If the 520 had been out when I needed to replace the 220, would I have got it instead of the 656? Yes, but it would have gone straight back if had frozen on any disks.