You may not have to go through all of that trouble to create a “faux 5.1” mix, as you say.
Many surround sound systems are run through amplifiers that can take stereo sound and emulate a 5.1 setting, so there is nothing you need to do if your homne theater has those options. You can prove what I’m saying by putting a cd into your system and fool around with your amp’s presets, and you’ll see that the stero sound can be channeled through all of your surround speakers to create different listening effects.
What you are talking about is really creating a stero sound into a true 5.1 mix. Once you start spreading signal to left, center, right, and rears, there is nothing “faux” about what you’re doing. 5.1 mixes won’t sound like 5.1 on a normal stero system, so if your aiming for that type of output, mixing for a 5.1 would be a waste of your time.