FYI you should be converting to 44.1 24 bits vs. 16. The DTS encoders accept 24 bit files.
Then I'm confused about the iTunes AppleTV part. I know how to do get DTS into itunes and play it back via a HT connected to an AirPort Express (and by the way I don't have to burn a CD to do it):
viewtopic.php?f=7&t=154but I seem to recall (and just did a quick test) that it doesn't work with AppleTV (Gen 2).
Would you please tell us more about your process?
Is your apple TV 1st gen or 2nd? That may be the key difference. Mine is 2nd Gen and I believe it converts all audio to 48Khz, thus not the bit perfect playback needed to stream 44.1Khz dts from iTunes.