If it the set up permits, you can remove your floor trim. Underneath, there is normally enough space below the bottom of the drywall to hide wires then put the baseboard back on. If not, it's easy to trim some off the bottom drywall off as it will again be hidden by the trim.
Once you get to the area you want a speaker, cut a hole in the wall where it the speaker will be. Outlet height for a floorstander or exactly where the speaker will be for a wall unit mounted like the picture above. It's very easy to use a fish to get the wire up to this hole and you can add an wall plate with the appropriate hole, terminate it on a wall plate with the proper ends, or just hide the hole with the speaker.
You can usually even get around a door in this manner as the door probably has trim running up and around it that can be temporarily removed as well.
The only drawback is that you might need to touch up some paint when you are done.
