Transparent PowerIsolator 8 with Mono Blocks

What you have been led to believe is correct. Get the MM for your amps, or use nothing at all on them. The last thing you want to do with a big amp is bog it down by not getting enough current to it. Even switching from a 20A breaker to a 30A breaker will improve the sound on your big boys.
I have a pair of 750's that I do that with.

I would check with Transparent. They have always been helpful to me. If they are the same and the cord is not capiured, you can get one and then upgrade to a better cord.

The more I think about it, I think there is a difference to the Isolator though, but can't swear to it.