You'd get some loss in signal strength for such a long run if you were using regular shielded cable, but not necessarily a loss of bass response. I don't know much about baluns, but I'm going to guess the one you picked is not a hi-fi unit. Did you check the specifications?
Incidentally, it doesn't make much sense to string a long cable run for a such a highly portable source...
This was a service call for a home we automated quite some time ago. He was having a party with a dj and needed a quick way to plug the dj system into the rack downstairs. we ran an extra cat5 to the tv in the living room so we just simply put baluns on both ends and put it into the audio switch i guess its a bit of a long run i was just wondering if anyone experienced a thin sound with rca baluns.