Ableton can split Stereo natively within the plugin chain.
Here are the instructions from Ableton Forum:
1. On the track containing a stereo file, create an Audio Effect Rack
2. In the Rack, create two chains, called "Left" and "Right"
3. Put a Utility on each chain
4. For the Left chain, set the Channel Mode chooser to Left
5. For the Right Chain, set the Channel Mode chooser to Right
6. Pan the respective chains all the way to their respective sides, either in the chain mixer or in the Utilities.
7. To compensate for the volume boost caused by Live's pan law, lower the volume of each chain by -3.01 dB (again, either in the chain mixer or in the Utility devices.
It seems like a lot of steps, but I was able to do it in a few minutes. The cool part is, once you build this splitter once, you can save it and use it for whatever effects you wish. Some people use these "racks" to split frequency ranges as well. Ableton is pretty darn flexible with this kind of stuff. I don't think Ableton is great for Acquas, though (on PC). The CPU seems to be high and some of them crackle and aren't usable. Nebulas however, work great, and I am able to get The CPU very low. Last night I had 37J Tape, AlexB console, AlexB full eq, and two of Tim's compressors on a track, using only 5 or 6 percent cpu. Nice.
I'll stick with Nebulas for now. New Aquamarine sounds great, but it eats too much CPU for me. Perhaps for mastering it would be good, though.