I'm trying an experiment to see if I can turn my ol' ICOM 735 into an "imitation K2/100" - I'm using the new AF1 audio filter with it and, yep, it makes a whale of a difference. I don't actually know if it rivals the K2's receiver (since I don't own a K2), but it really does sound as good as my K1's receiver! Terry Wilkinson W1BPJ