ground loop questions

sounds like you currently have youw monos pluggged into a duplex receptacle...this is causing your loop...yes, best bet is to run 2 dedicated lines and receptacles, and plug 1 thing (in this case each amp) into it. using a heavy gauge ext cord should be fine, but be sure, the longer you go, the heavier you need...just how long do you need. I would run the line regardless...it will not only fix the loop, but also improve noise floor, background noise, details, the usualy improvements.

Be sure BOTH lines are on the SAME phase.For monoblocks. Your frontend and digitail you can seperate

I don't understand what it means to have both lines on the same phase. Does it require making an extra wiring connection? Can you explain?

positive to positive, negative to negative

Jaf2290 - Plugging components into a common receptacle is a good way to minimize the chance of a ground loop, what you are trying to avoid is a difference in impedance to ground between two components. This is also why a heavy gauge ground conductors are sometimes helpful (keeps everything at near zero impedance to ground & so minimizes differential). For what it is worth, some manufacturers reccomend plugging all components into a common power strip as a starting point.
Phase in household wiring is typically thought of in terms of which side of the incoming 220v supply you are tied to (the center is usually grounded so you end up with two 110v sides or phases) , positive and negative are usually thought of as refering to polarity.
Viiu - good luck, ground loops can be a nuisance. One thing to remember is that a ground loop can't come from one component. To have a gound loop you have to be tied to ground at two different places (i.e. there has to be a loop for current to flow through), so you should be able to break the loop (and eliminate the noise) by breaking the connection at more than one place.