Great additional info! Let's see if we can summarise then:

Theatrical release - 70mm 6-track and Dolby Stereo

1992 special edition laserdisc - Dolby Surround (probably from Dolby Stereo master)

1995 THX laserdisc - 5.1 AC-3 and 2.0 PCM (based on 6-track 70mm master)

1999 DVD - 5.1 (actually 4.1) and 2.0 AC-3 (based on Dolby Stereo master - both mixes sound exactly the same)

2003 DVD - 5.1 AC-3 and DTS (new mix with Director's Cut variation)

2010 Blu-ray - 5.1 DTS (new mix with Director's Cut variation), 4.1 AC-3 (who knows? ;) ) and 2.0 AC-3 (very 'smooth' sounding - since it's available for both Theatrical and Director's cuts, it's probably a compatibility-minded downmix of the new version)

Feel free to add or amend. The laserdisc is looking more and more important, but the lack of info on that 4.1 is deeply frustrating - I'll delve through HTF's message boards to see if something ever came up (and doesn't Charles DeLauzirika host a forum there?)