Murata filters are not known for good shape factor(6db//60db) . When
stacked in series losses mount rapidly. And they seem to have a lot
more noise when compared to crystal or mechanical IF filters. Have you
tried to build a crystal ladder filter? Very effective and MUCH cheaper
than any other IF badpass filter ,and Inrad is not the costliest-
KVG,Collins etc.may set one back many hundreds of dollars...