You'll find the S350DL to be very close/on par with your Superradio as far as audio quality and reception goes, it's probably the closest modern analogue of the old GE.
Any interference your fluorescent lights or area in general produces would be picked up by the radio you have now, so if you're not hearing any local noise, then it's not an issue. The fading you're hearing is due to your distance from the radio station; the signal is too far to travel in a line-of-sight path, so you're getting part of it that's reflected off the atmosphere - as atmospheric conditions slowly change, your signal slowly fades in and out with it. An antenna may not entirely resolve the issue, but it can greatly increase the amount of time the signal is present/not faded. Since you already have a very good radio, you'd need a very good antenna to make a notable difference, I'd recommend the CCrane Twin Coil. The CCrane's modular system means the actual antenna element is on a long ~10' wire, so you can set it on a windowsill or even outdoors. It's worth it if you have the ~$90.
Another more direct solution would be a web radio setup; if your house has wi-fi, you can just use a laptop connected to a good pair of speakers to playback any radio station's internet stream. This eliminates reception issues entirely, but unless you already have the needed elements, is too pricey to start from scratch.