What's longest i/c's can be run?

I run about 20 feet with no problems. I have used both single ended RCA and balanced. The balanced have a little more gain, but other than that not much difference. I believe you are always better to run longer interconnects and keep your speaker cables short as possible. There would be a greater deterioration in sound with long speaker cables than long interconnects.

I fully agree with the above noted comment. Keep the speaker runs as short as possible and your interconnects can be as long as you want. My experience is quality cable is an important factor in letting your equipment reach it's potential.

As long as you use a low capacitance cable you should have no problem with long single ended runs. If you go balanced it will make no difference at all what the length is and it is generally thought that with balanced cables the quality of the cable is not as important as with a single ended cable. Some balanced circuits will have more gain, but that is only an issue if you are not using a preamp (direct out from CD). There are some tube preamps (Counterpoint comes to mind) where you may experience some roll off of the higher frequencies with long cable runs, so you might want to check with the manufacturer, but I've never had a problem with this and I've had several tube preamps.