Choice of Wire for Dedicated Line

I agree with Lak and Rcrump. Having dedicated lines of around 30A (for the 230V supply here) appears from my experience to be all that is required in the wall - OFC etc makes no discernable difference. Using 5 to 10 feet of good power cord seems to do the rest. Note that having dedicated lines will accentuate the differences between good PCs and stock PCs. Using significantly longer lengths of power cord or more costly cable in the wall have no great effect. One often overlooked issue is that even the standard Romex is VERY directional. Try it both directions before you put it in the wall. The difference is large - so don't gamble. A further overlooked issue is the mains fuse. A poor mains fuse will do more damage than any noise the cable will pick up. The best in my opinion are the ceramic fuses. The glass ones are hopeless. The breakers sound OK until they get 6 months or more old. One of the big advantages of the ceramic fuses is also you can take them out and clean and tighten the contacts. This makes a big difference, as does getting you electricity supplier out to clean and tighten the contacts where your drop feeder is joined. An then there is the grounding arrangement...

Jeffcott. I have found that if you use stock PCs then when you put a dedicated line in, that you will hear an improvement in dynamics and soundstage size, but you will find the sound can be brighter and with a coarser grain. Systems that sounded acceptable with stock PCs, became more fatiguing to listen to with a dedicated feed. When decent PCs are used for every component, then the overall improvement over a non-dedicated feed can be stunning. I have experienced this with around a dozen instalations.

The Romex you have in the US may be different from what we use in NZ (and we call it TPC). But of the three types I have tried, each was quite directional. When used in the wrong direction the sound was relatively thin and flat with a fat indistinct bass. When used in the right direction the sound was more vivid and natural, with better depth, better bass articulation and rhythm. What I have done each time is run the cable from the switch board to the components through the house (ie. not in the wall yet), in one direction and then the other. The difference in sound has been quite marked with each of the three makes of cable available here.

I won't comment on grounding. For a start the topic is big, and has been covered elsewhere in Audiogon. More importantly, when reading through what Americans found was best to do I discovered how different the 115V supply there is to the 230V supply here - with critical differences about ground arrangements.

The stuff we get here (New Zealand)is directional from new, and it is possible that the Romex you get there is manufactured differently, and may be of quite different quality. The stuff we get here is usually called TPC, not Romex, and as some will know, stands for tough pitched copper - ie. made by archaic methods.