You can conceal the wires behind moldings at the ceiling/wall joint -- crown or something else that fits in there. I made a small molding that fits beneath the crown that was already there, with a groove in the back to run the wire through, and nailed/caulked it just under the crown. If you look, and know it's there, you will notice it, but otherwise it is fairly unobtrusive.
I ran the wires up through the wall from the receiver, pulled them out at the top, back through the molding, then hooked one spkr to one wire, fished the other up through and across the ceiling (had to cut some corners out to do this as mentioned above) and then down a bit to the other spkr. A bit of spackle and paint and it looks fine.
On new construction I think the idea of a box with a cover is the best, and maybe run some conduit to it so if you ever need to run anything else, it will be easy.