Question:  I'm not sure which model bandpass filter to get, the legacy models or the high performace models?

Answer: Check out this tech bulletin on using band pass filters.

Question:  How much attenuation do the filters have on an adjacent band?

Answer: Check out the VNA plots on each individual filter's webpage, in the photographs.  Click the pic to enlarge it so you can read the numbers.  Legacy models have around 20dB to the adjacent non-WARC band, and high performance fitlers have 35-50dB, depends on the model.

Question: What if I'm running an amplifier?  They only have a 200w rating.

Answer: Correct, do NOT run on the output side of the amplifier!  DO place the filter between the radio and amp.