There are usually ridges on one side of the wire if it's figure 8, I think that's commonly used as the negative, otherwise, use your multimeter and mark the ends, as you suggest - as it sounds like you know, your polarity on your speakers is important, otherwise the cones move the wrong way! You can also use multistranded lamp cord as long as it has the same or better rating. You are definitely correct to go with wire of the quality you describe, it will meet the codes but will not cost you like Mon$ter cable which will *NOT* sound any better. Trust me, and all the countless engineers who say so, on that point ;)

There was a discussion here on this exact subject a while back. I hope your inspector is wrong because the advice given here was CL3 was the type wire to use...and that is exactly what I used. My speaker system called for 14 AWG wire, but due to the length of some of my runs, I bumped it up to 12AWG. That would be a very expensive mistake for me to have to fix at this point. I'm sure you will get some very expert advice from some of the guys here. But if nothing else, I would politely ask the inspector to cite the code where you can't use that cable. But remember, each locality can have it's own set of "adjustments" to code...

We put them in the kitchen when our house was down to the bare wall studs also in the renovation. We used separate audio zones...we took 3 walls down to create a huge great room that is half that particular floor of the house. We put the plasma TV on a pull-out mount over the fireplace, so you can pull it out, then angle it towards the kitchen to watch TV while cooking. The main "guts" of the system are kept in the living room area...multi-zone receiver, dvd player, cd player, cable box, etc. The cables are bundled together and go into the wall in a neat and clean small box that is hidden behind the console. The living room part of the great room has the surround sound, with the rear speakers placed in the ceiling so they are hidden. The second zone was to be the library/music area, and is wired into the bookcases. I never put speakers there, as I was able to get a great deal on a Martin Logan surround package with electrostatic front speakers, so I could combine high end audio with surround movie, and save on not having to buy one extra set of speakers. The kitchen is the third zone and we installed Martin Logan ceiling speakers. There is a separate volume control in the kitchen wall, but frankly, we tend to use the living room speakers and volume control. The ceiling speakers are used mainly to turn up the sound when watching TV or listening to music while cooking with the hood and other noises going. But in hindsight, we probably could have not gone with them, as you can hear the living room system clear as day from across the great room in the kitchen. But because the walls were open to the studs, it wasn't that much more to install them at that time, so we went for it.

Ron, you're absolutely right that it depends on the speakers' efficiency. But if you measure the actual power output of your amplifier at normal listening levels, I think you'll find the average output even with sealed acoustic suspension speakers isn't more than a few watts. That extra power is there to handle big peak demands, like a bass drum hit. Bar perhaps Fisher, the typical console stereo of my youth (remember The Voice of Music? Capehart?) could seldom produce more than 2 to 5 watts per channel of continuous power, but it managed to do a more or less adequate job for undemanding music in the average living room. You could turn those boxes up enough to make mom cover her ears, and not even be at full volume yet. :) A little anecdote might serve here. The old timers who said 20 watts was plenty for a midsize auditorium were right. Many years ago, I volunteered to provide audio for a youth dance concert. I reserved a PA from a local rental agency, but I misunderstood their closing time on Friday, so I missed picking it up! Any port in a storm, so I took a late 60s vintage integrated amplifier (noisy bipolar transistors, undersized linear power supply) and 2 Dynaco A25 speakers (a moderately efficient ported bookshelf design). I knew the amp was good for just under 10 watts of continuous power per channel into 8 ohms at clipping, because I'd measured it. The dance was in a high school auditorium. We're not talking about the gigantic megachurch sized auditoriums of today's "learning centers," this was a more modest sized place built, I would guess, in the first third of the 20th century or a bit after. The auditorium was typical of that era, a rectangular box, orchestra and balcony seating, bare concrete floor, unpadded wood seats, big wood windows, solid plaster walls and ceiling. So it was fairly live, thank goodness. It worked mostly fine, at least for the audience. There was plenty of volume out in the house, though without stage monitors, the dancers complained that they had some trouble hearing. So, 20 watts indeed can be auditorium power. And average power in home listening is seldom more than a few watts.