Terry - the filter doesn't have a mid point. A regular treble control allows you to boost or cut the signal around a fixed frequency, and indeed the mid point on a treble pot is often marked as 0.
The Alembic filter is known as a low-pass filter: the filter pot lets you to set the cut-off frequency, and all frequencies above that will drop off at a fixed rate. The highest setting is 6,500 Hz, which is the top of the relevant frequency range for electric guitars and basses and associated amplification.
The design of the low-pass filter creates a small natural boost at the cut-off frequency. The Q switch increases that natural boost, at whichever cut-off frequency the filter is set.
I'd agree with the amp settings. You don't need to turn up the volume too much to get the balance right. As to headphones, be careful with the types that offer extended bass response - probably less suitable for getting the balance right.
Finally, do not forget to play around with pickup heights, especially if you want a beefier response from the bridge pickup. After experimenting with a FatBoy recently, I found that raising the AXYs closer to the strings helped bring out more of the beast in my Spoiler.
