Serato Scratch Live Ableton Bridge

My question regarding The Bridge, and I am not sure if I've seen this discussed anywhere, is this:
So, you are using a TTM57SL to control and play SSL, and you have Live running as well. If you are using both channels of the 57 for business as usual, do you need a separate audio interface in order to get the sound out of Live and into the auxiliary input on the 57? Or can you set it like the SP-6 player to just play it through the Master?
And following this train of thought - if you only DJ with 2 channels, and want to have the audio from Live on a separate channel but synced to your SSL tracks, would it make more sense to pick up an SL3 and an Empath (or another 3 or more channel mixer) and ditch the 57? So in this case, the question is as such: Can the audio from Live be routed through output 5/6 on the SL3?
And can The Bridge system handle running Instant Doubles of the ATC?
Sorry if this has been addressed somewhere else, but I haven't seen it, and I can't find any mention in the literature that is currently available regarding this.
Serato

Serato Scratch Live Ableton Bridge Free

Mar 09, 2011 The Bridge is the result of a partnership between Ableton and Serato to create a way of interfacing their Live and Scratch Live products. The concept has been out for around six months, but it’s fair to say the concept has not yet really set the world on fire. A lot of resistance is based. Garageband download all available sounds.

Serato Dj

Oct 07, 2010  On the Ableton panel inside of serato below the ableton Master track is a little set of routing buttons. L, R, and Mute. L and R choose weather Lives master out is coming out of serato SL's left output or right output while being used in internal mode (that is, using Live but 'without' it actually being loaded onto one of serato's decks). At the foot of the Ableton side of The Bridge you launch both programs and an Ableton Live Transport Track appears in your Serato library. Dragging the Transport Track on to one of the virtual decks means you're now ready to use the deck to control Ableton Live's tempo and playback. 1st page The Bridge provides Ableton Transport Control (ATC), giving you control of your own multitrack productions with a turntable, CDJ or ITCH controller.Drag an Ableton Live set onto one of the decks in Scratch Live or ITCH. Note: These are the minimum specs to run The Bridge, for best performance and for professional use we recommend a higher spec computer. Note: The Bridge is not supported by Ableton Live Lite, Ableton Live Intro, Ableton Live Akai Professional APC edition and Ableton Live Launchpad edition. Ableton and Serato bridge the gap between music production and DJing with The Bridge. The Bridge requires Ableton Live/Suite 8.2 or above and Serato Scratch Live 2.1.1 or above. Learn about The Bridge. Refine your mixtapes Record your Serato DJ performance as an Ableton Live Set, complete with song placement and fader movements. At the foot of the Ableton side of The Bridge you launch both programs and an Ableton Live Transport Track appears in your Serato library. Dragging the Transport Track on to one of the virtual decks means you're now ready to use the deck to control Ableton Live.