Calculating Capacitance / Rolloff Frequency for Across the Line RFI Supression
Well, no, you don't want your filter to have a low impedance at the line frequency, because then you'd be wasting a lot of current through the filter. So cutoff numbers in the high audio range make sense in general.

It's much more important to keep stray RF (455 kHz and up) from the AC line from getting into the sensitive RF and IF amplifiers, and also keep RF from this receiver out of the AC line, to prevent transmitting interference to other receivers.



Just a side note about notation: Old parts used "mF" for microfarads (and mmF for picofarads), but nowadays we now use that to denote millifarads, 1000&times; larger. You really should be using uF or &micro;F here, just to avoid confusion.