I think the issue with docks made for earlier nano's is that the dock connection is offset. On the 6G's, the dock connector is centered. Check out this LINK.
I think the Minidock looks pretty cool. You'll need to supply your own AC/USB adapter, which Apple sells for $20 (i think).
If you want a speaker, I think they all work. Just be careful of ones that aren't designed for the 6G. We have a logitech speaker for the Classic/mini. The 6G will fit, but if I have the adapter for the mini on, it's very difficult to remove the 6G.