MONSTER question

I use one with a big Panasonic Plasma and it does make a better picture...worth the money for that....if the current gets too high or low it shuts off and protects your gear...mine did that once...as for audio performance I didn't notice any improvement to the sound system I rigged up. A better device would be something like an Exact Power EP15A that does all the stuff the Monster does but keeps the current locked in at a steady voltage (my power fluctuates alot) and this will greatly extend the life of your equipment. So for the small amount the device costs I think it's worth it.
Larry

(isolated grounds).

What do you mean? Ground should be connected to neutral at the electrical panel in the house?

Monster Power Center HTS 3500 MKII for my theater

I have no experience with this model. However Monster power conditioner bars (surge protection and filtering) had an effect on one of my digital components. I note that this product does no line conditioning.

I think you have to try it and see. Everyones situation is different. What works for someone may not work for someone else. I tried several conditioners before settling on an industrial product from APC which does proetction, filtering and line conditioning (maintains the voltage to the gear within tighter tolerance and automoatically adjust when the electrical power sags due to heavy aird conditioning loads or daily variations). APC make the Rotel branded conditioners. You may be surprised to learn that power conditioning is not rocket science and industrial products have existed for many years (long before audiophiles became concerned about this), in fact some of the audiophile products are simply OEM products rebranded with an audiophile nameplate.

Prior to making any decision - check out Richard Gray power conditioners...