What's the reason you would want an oscilloscope for such a job, instead of a spectrum analyzer? That's usually not the right job for that task, even if it has FFT, the signal levels for a scope is much higher, the dynamic range is much lower, you don't have 50 Ohm termination on the low frequency scopes, the input capacitance is high and so on. I would guess even an SDR would be better, or a low cost spectrum analyzer.