In my experience with sound bars I have found that if you are just using it for normal TV watching they will be better that TV speakers but thats about it YMMV. Movies...not so much. Bose has a nice three or four piece system that doesn't use rear speakers that sounds really good and may work for you. You may also try removing the rear speakers in your existing setup. If you are just set on a sound bar though I would definitely go try a few out in the stores before just picking one up. I bought one at Walmart and promptly returned it the next day.
If you don't want to fish your walls I have seen people remove their floor or ceiling trim, run the wire behind it, the reattach it to hide the wire. Lowe's also sells some type of plastic channel you can use to hide them and paint over it. That may get expensive for long runs though.