I will definitely have the cat5 drops done for each room.
As far as controlling music...I just run iTunes and use my iPhone to run the Remote app and control the music anywhere I wander, via the wi-fi network. Works like a charm, and it's "free"!
I guess my main question was really, is it stupid to run 50+' of RCA vs spending more and converting it to Cat5 along the way. If there's nothing really wrong with it, then I'll just stick to RCA. Today, I run about 30+' of RCA from the PC to the receiver, but, I am just going down through the floor and across the basement ceiling and back up...ghetto install but it works and it doesn't matter. The new house would have the wires run through the walls and possibly near electric wires, etc. Didn't know if cat5 was a lot more reliable or anything.