Why not use a power conditoner

I understand the convenience of using a separate ISO breaker box and the ISO Torrid Transformers they use, but do you not get the same benefits using a high quality power conditioner such as MIT Z isolator or the equivalent.
Do they incorporate the same torrid transformer principles only on a smaller scale.
I use the MIT Z-Isolator the transformer is large and it only covers two outlets.
Does it matter where you attempt to filter the power.

Which brings me to my 2nd question:
I as quite a few other people have a ground loop problem even if I just turn on my Mono blocks with no other equipment turned on I have a hum/buzz (Less if I used the switched outlet on the MIT Z but still there).
I even disconnected the IC to the pre-amp, same hum.
Why am I getting this hum even though nothing else is connected.
How does one achieve this elusive silent background.
(My Monos are Manley Snappers, The Power cords from the Z-Isolator to the Monos are MIT Z- Cord II's and Signal Cable for the power to the Z-Isolator)

Thanks