I have to run some cat6, speaker wire and HDMI in ICF. I bought some proper device boxes that spike into the foam when installed. My concern is that the wall is drywalled. I'm not sure how I should go about cutting and replacing the drywall. I could cut a line between those plastic "studs", but that means the replacement piece won't be strongly anchored. Conversely, taking the whole sheet off might be worse if glued. Could I just cut out like an 8" width going up the wall and screw and/or glue a new piece into place? I'm also a bit concerned if I need to avoid cutting those plastic "studs" when cutting lines for wires. Any thoughts?

We normally just place low voltage flexible conduit where CAT6, coaxial cable and HDMI needs to be run. Of course, you should normally do this before you install the drywall... After the drywall is installed...I think I would just neatly cut out a vertical section of drywall that was wide enough to allow placing the conduit between the studs and also wide enough to allow securely screwing the drywall to the studs. It is always best to avoid having to cut horizontally through the studs and there hardly ever is a need to do that...but this can certainly be done if needed.

Thank you very much for your reply sailawayrb. I wasn't sure if I was going to get any feedback

In one section, I'm looking at installing a 3 gang ICF box (found them at my local specialty electrical store... they were tough to find) to run wires for this:
http://www.monoprice.com/Product?c_id=109&cp_id=10425&cs_id=1042503&p_id=6907

In the other section, they'll be single boxes (ethernet and/or HDMI).

So if I understand your suggestion correctly, I should cut out a 16"ish wide (plastic stud to plastic stud) section of drywall from where the box will go, up to the top of the wall. I was wondering if that'd be the best approach, but locally, I've heard people suggest just (as best as I can) cut out around where the box will be and up the wall, and just crackfill in around it. But my concern was that the ICF device boxes have exterior flanges to ensure that it is flush against the wall, and I figured that having a nice piece of drywall around it would go the extra mile to keep it in place.

We typically use standard plastic electrical boxes, hot knife out hole for box, and then screw box to nearest adjacent plastic stud. For wall sconces, etc., requiring additional support, we use metal electrical boxes anchored directly to concrete. However, you don’t want to do this for boxes using GFCI if you are using a Ufer grounding system. Depending on the ICF block that you actually used, the studs are usually every 6” or 8”. So yes, a 12” or 16” width allowing fastening in two adjacent studs would be my recommendation. Again however, we have always done this BEFORE placing the drywall and not afterward! Hopefully, you will get more feedback from those who have had to deal with this issue first-hand.

In our ICF house, I ran wires from the main floor down to the basement by cutting a hole for the box upstairs, and an access hole directly below it in the basement. I heated a 1/2" ball red hot and dropped it in the upper hole as far back as I could get it. About 30 seconds later, the hot ball drops into the access hole below. Put foil in the bottom hole, or lose the ball forever. That's for vertical holes; not sure what you should do if going horizontal. Note- if there's a lot of concrete oozing between your blocks, the ball will stop.

Sail
I'm curiuos as to why you don't want to use a metal box directly attached to the concrete when using a GFCI and UFER?

Sail
I'm curiuos as to why you don't want to use a metal box directly attached to the concrete when using a GFCI and UFER?

Nashvegas, we experienced nuisance GFCI tripping likely from the creation of multiple ground loops. Has your experience been different or do you have a solution for this?

Sail,
I don't have the experience yet, but will soon as I'm currently roughing in the electric. I may switch to weathertight PVC boxes on the outside receptacles if metal is a problem. Anyone else had an issue with this?

Never had a problem with metal box in residential or commercial construction.
That said, the plastic will give you a slight thermal break.