You should note that David Berning has done some improvements to the latest versions of the ZH-270. This may explain why some older versions are popping up on the market now.
The newer version does appear to be more powerful than the old version and also faster.
The ZH-270 is a great little amp, I like it a lot. It does however not have "unlimited" amount of power so it is not a good match with the most difficult loads.
Karsten
