Impact of Ferrite Chokes on power and signal

I wanted to get the collective wisdom about use of ferrite cores on
power cords.....and also in the signal path. I just ordered
a bunch from:

http://www.allelectronics.com/cgi-bin/category.cgi?category=
235

I also ordered a couple of these to try on the output of each
of my monoblocks:

http://www.empiricalaudio.com/
frtweaks.html#Speaker%20Hash%20Blockers

I figure i'll do a lot of a/b comparisons with and without
ferrite in various spots...but i'd be very interested opinions of other tweak geeks!!!