Please show your work and your notes in the margins. I'm considering going that route but I am a little intimidated with the various hardware, software and adjustment methods that plan requires. I like the SMS-1 because it's plug and play. I'm not sure I'm ready to play with the Big Dawgs yet.
For 500-600 bucks you can get the dbX with a microphone that basically does the same thing as the SMS with all the processing gadgets too...eq, limitors, compressors, sub-harmonic synth, etc.
Kind of a lame video, but it gives you the basic idea.
Both the Behringers and dbX's aren't too hard to use, it just seems a bit intimidating from the start. I've used both as crossovers in venues, limitors, etc.
Honestly I think a big benefit to the dbX (and I think the Behringer does this too) is time-aligning, which helps get your tops to match with your sub better.