cable degredation audio/video

Here is the deal.
I'm into 2 channel audio and have an amp/pre and cd player in the front of my room.

In the back I have my cable box, dvd player, receiver and projector.

I have tried running rca cables from my receivers output to my preamp (which has a HT bypass) but I get a TON of hum in the line. I assume its because of the distance of the rca's? they are about 20 feet.

I was thinking that I could move the receiver/dvd/cable box to the front of the room so the RCA run would be much shorter to the preamp. In which case I'd need some 20 ft long runs of component video cables to get back to my projector.

Or I could just move the receiver all the way up to the front and get a really long (20ft) optical or coaxial cable to get the sound from the dvd player (which would be back by the projector!)

which setup do you think would be best?
where do you think the hum is coming into my system?
Perhaps the hum is from your cable box - try disconnecting it and see what happens. Not an unusual problem.
or ground loops
what are ground loops?
I'll try the cable box thing when I get back tonight