To clarify... the SMS-1 has a variable low-pass output, but the high-pass is fixed at 80Hz, 12dB/Octave.
If you intend to run your Vantages full-range, you'll probably want to set the subwoofer to only receive a frequency range that augment's what little the Vantages are missing, at least when it comes to music. Something around 30~40Hz would be a good starting point to isolate the sub to just the bottom octave.
For movies where the signal is divided somewhat already by the mastering process, you may want a dramatically different setup... maybe sending more to the subwoofer and less to the Vantages. If your processor doesn't have the flexibility, remember that the Depth can connect to your processor with BOTH the .1/LFE and RCA stereo. ie: Run the subwoofer (LFE) output from your processor AND stereo mains to the Depth. (You may have to split your stereo main outputs if your processor doesn't have two sets). The Depth will use the LFE signal when present (watching movies, tv, etc) and the stereo input when it's not present (with the processor in bypass mode).
Sorry if this is confusing... it's basically what I do with my Vistas, Descent, SMS-1 and Outlaw 990 processor and it works nicely. Of course, it means I only get the benefit of the SMS-1 for movies/tv, but the Descent sounds great without any further processing in my room.
- Jason