Hello Microo1234:
The recivers that have a good IF Filter like a crystal filter, or Collins Mech filter, usually have great selectivity, and sensitivy. The Cats Meow is a good ham rig, I use a Icom 746 that has great IF Filters, and
(DSP) in the IF for more filtering. It allows stations on USB to be significantly attenuated when using LSB.
Bit on a more pratical way, I look for a radio with with a good noise blanker, RF Gain, and (ANL) Automatic Noise Limiter, and hopefully again a Real Crystal Filter in the reciver IF circuit. Being able to turn down the RF gain of the reciver is also a big help in some noisey conditions, and attenuating adjecent channel stations that are loud. Some but now all radios have gone to a FET front end that has a cleaner output that has less noise and such.
Mobiling down the raod while listening without engine, fuel pump, heater motor, ignition module, and alternator noise is a real treat. Again a NB is agood call.
There are DSP Filters out there that go between the radio and speaker, that the advertising says it helps reduce noises.
Hope this helps
Jay in the Mojave