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.
