It doesn't auto tune. You'll have to get used to the 1000 numbers. First thing I do whenever I set up my systems is delete all the SD channels, shopping, religious, PPV and channels that aren't in my package. That would include channel 3, leaving only the HD version in the high numbers. I rarely use channel numbers anyway, only the guide and favorites on the DVR or favorites on my remote. On my system they're very easy to remember anyway. 4 -> 704, 13 -> 713, etc. Never been a problem for me.

X1 isn't a bad system, so Tivo wouldn't be that big of a change for you. It was a huge change for me.