Thanks Beckp,
I'd reviewed your post & others I'd found from TC30 only owners but none gave a true assessment of build & ergonomics that are so poor on the 520. Some general reviews say TC30 buttons (esp numeric) are better spaced than 520/550 but from the pics they look identical. Also the height of the channel & Vol controls are poor on 520/550 so hopefully this is better too. These issues and the "creaking" (cheap) of the 520 is why it's a short timer.
If the HK isn't better in these areas, the 550 addresses the worst of the issues and I don't need color or 8 LCD buttons.