For plain old 2 channel audio. Is 50 - 60 feet too far? The plan is to tie my main system into an old receiver and speakers sitting in my living room. This is just for background music, not serious listening. So I don't care if I lose a little sound quality. But I didn't want to buy the cable if it flat out won't work.

I have run analog audio, digital audio, and composite video over 80+ feet of Belden RG-59[AU? U?] at various times over the past 25 years. The signal quality is very good. The only problem I am aware of is if the ground potential for the equipment is different at the two ends. This might be the case if your house has more than one elecrtical panel or you are using heating or plumbing pipes as ground.

For plain old 2 channel audio. Is 50 - 60 feet too far? The plan is to tie my main system into an old receiver and speakers sitting in my living room. This is just for background music, not serious listening. So I don't care if I lose a little sound quality. But I didn't want to buy the cable if it flat out won't work.

That should not be too far at all. Just buy quality, well shielded cable, from BlueJeans or the like for lengthier runs.