QUOTE(Zulu.Walker @ Apr 6 2007, 10:40 PM)

For windows, use Nuendo, separate all channels into their separate timelines and do your stuff, rechannel your 4 stereo tracks to a 7.1 mix, use the main track for for all channels with slight adjustments and send the other 3 stereo tracks to front/side/back and reprocess main track with LFE to add the .1. Overkill? Nuendo is used for multitrack film scoring with support for everything. Not really popular, but you wanted overkill here it is. Don't forget to use the advanced sound revirtualization to hear all the tracks you want in a complete mix.
For Mac, Logic Pro would work with an XSKey. Else, Logic Express would be ok. I haven't personally used Ableton Live! as I don't have the hardware, but I've had some experience with ProTools but haven't tried multichannel audio scoring/mixing with it yet, just a studio recording.
It's up to you to read all the pertaining material for you to use these programs to their fullest. I can't help you with your project, maybe it'll be easier for you to encode your stereo tracks using an audio muxer like Scenarist AC3 encoder, but you won't be able to manually adjust the tracks there, just encode.
If you haven't used any of these programs yet, good luck. Nuendo has one of the steepest learning curves I've ever encountered with an audio app, but I've no complaints on its functionality. Make sure you have an ASIO2.0 card if you plan to use it, not much fun having skipping audio and sound ramping up in speed.
I'm guessing you mean not popular for doing specifically Audio editing only in the app.
Otherwise Nuendo is popular for Video Production and Music Production on wich i prefer over cubase on Windows to use.
Other popular Audio editing software is Wavelabs, Soundforge, Adobe Audition, Audacity and for Mac i haven't used much yet but Soundtrack pro along with Audacity again.