Yup, visible wires gives it a rather Busch League appearance imo. Gotta hide them any way you can.
For the plasma, I added an outlet behind it to power it, and ran two runs of video up through the wall (The basement was unfinished at the time so running them up wasn't too bad.) then looped them over down in the basement area and ran them back up to go into the media box next to the couch.
The speaker wire was pushed between the baseboard and the carpet (you can usually hide quite a bit of wire in there depending on how tightly your carpet was installed) they come out right behind each speaker and this short run is just pushed in/buried into the carpet between the baseboard and the speaker so they are not seen from the room.