Jdubs,
I'll let Occam chime in on this one, might want to send him a pm directing him to this thread. In any case, I have always used Felixes before the primary of a transformer, i.e. right after the AC outlet in all my projects. I've always found an improvement as well. Dynamics are increased, high end is always smoother, midrange is more open, and microdynamics are improved. To quote from the late Allen Wright, basically there is an increase in the 'downward dynamic range.'
Best of luck,
Anand.