The only thing more difficult than chasing hum (noise) problems, is trying to chase good FM signals. I understand your problem, and the only solution I can think of to try, beyond what you have already done, is to get a FM antenna (outdoor type) and put it in the attic of your Condo. If you do not have access to the attic, I do not know what to suggest. The reason the outdoor type antenna's are more effective, are the fact that they have much better front to rear rejection. Some of these are referred to as "ghost killers." These antenna's have specifically high gain in one direction (and sometime ONLY for FM signals!) and low gain from the sides and rear. This design I am speaking of will more likely provide enough signal for stereo reception, especially if CAREFULLY aimed at the FM source. If you are trying to receive from more than one location, you will need a motorized rotor, with a compass control to locate the correct tower. Best luck!
FM Reception
Currently I am using a Terk with my tuner upstairs and a dipole downstairs. My reception is awful to the point that all FM must listened to in mono. I live in Benicia near the Carquinez strait (by San Francisco) so I am surrounded by hills and may not have a clear shot at an FM transmitter. The signals appear to be strong so I suspect multipath interference. I live in a condo so an external antennae is not feasible. Any suggestions?