After repainting our living room wall and trim, my wife was reluctant to re-install speakers mainly because I had never gotten around to dealing with the ugly wires running up and across the walls. Didn't really want to go to the trouble of running wires through the walls and into the attic, so I was left with running conduit.
I went with urethane moulding because it was cheap and light weight. I first thought I would double-stick tape it in place, but that wasn't adequate so I had to tack it with tiny nails. This is much lower profile than any of the conduits options I could find, so even my wife was satisfied with the results. The moulding was about $2.50 for 8' vs $7.50 for 5' of pre-made conduit.
I rabbited out a channel on the table saw carefully because this was such a thin piece of urethane it was pretty fragile.