They are essentially pre-amps.
There are a few options out there.
Might help you decide.
I don't believe the SB Audigy SE will allow this.
So do the sound processors replace the amp I already have, or is this just a supplemental piece of equipment?
Yeah, I saw that last night on my search, but as a newb on car audio, didn't fully understand what I was looking at.
Is the the Alpine 701 you are referring to?: Click Me
If you go with the Alpine you will need the RUX and the PXA.
You're also looking at a few hundred bucks ($400+)...so you may or may not be in the right price bracket.
You could also use the alpine pxa-h510. Quite a bit cheaper than the 701 and it has its own wired controller.
No FAQ because there's just not enough people asking about it.
Feel free to write up a thread when you find a few.
Assuming you're still running Roadrunner, the winamp linein plugin will allow you to play the SPDIF input. You have to change the sampling rate from 44.1 khz to 48 khz but other than that it works like a charm.