Which one's a better encode? 5.1 or 2.0 track? (DVD Source)

[Cheburek]

Quite often a dvd will have several audio tracks: DTS/5.1 Digital/2.0 Stereo Surround. For purposes of encoding these tracks to mp2 audio, which source will sound better for SVCD ouput audio?

Since the original DVD 2.0 track is optimized for 2 channels and VCDs/SVCDs are 2.0 sound, does it make sense to always encode from a 2.0 source rather than 5.1 (when possible of course)?

Also, are there any programs capable of encoding from a DTS track?

[adam]

Using open source software, its questionable whether you could possibly do as good a surround sound downmix as what the professional studios do. Even if you could why spend the extra time doing it? If there is a 2.0 surround track on the dvd then use it.