Hopelessly vague: "get the most out of my SWL experience?"
If your antenna consists of a log periodic at 100' on the east coast near a VOA transmitting site, an optional roofing filter might be somewhat useful... occasionally. What modes are you referring to? What broadcast services do you listen to? I can see one being useful sometimes for listening to broadcasts in the 40 meter ham band.
Heck, I sometime SWL with one of my 1930s-vintage Zeniths for nostalgia sake. They hear pretty darn well with a hunk of random wire for an antenna. For most listening purposes I'm sure a barebones K3 would be vastly more than adequate.