1) The box itself has no AVI support of any kind, so no channel will be able to support AVIs.
2) I have an original N1000 box and the latest XDS box and I notice no difference in their performance. The newer boxes have more RAM and flash which allow improvements in some areas, but nothing that would affect MyMedia.
If streaming your own videos of different formats is of great importance to you, this probably isn't the right box. However, if you don't mind encoding them in a Roku-compatible format, then I think the box works just great and it's hard to beat the price. By the way, if you can run Python on your NAS then it can serve as the MyMedia server.
-JT
Roku Community Streaming Expert
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