what's going on with specs?

It looks like the BHK 250 has more distortion 20 - 20 k than the Parasound whether it's audible  I have no idea. Of the 4 you mention paired with the Elac I doubt you could hear a difference, the BHK perhaps since it has tubes tossed in probably why it has more distortion. 

Music is art, music reproduction is 100% science. 2 amps that measure the same as long as they are used within their limits will sound the same. 

Of the 4 amps the OP mentions maybe and that's a long shot maybe one might pick out the BHK 250 over the other 3 between the other 3 I know I wouldn't be able too.

Signal over noise and distortion. Power v distortion full load at 4 Ohm both channels driven. Frequency response. Get 2 amps that measure about the same driven below clipping will sound the same or at least so close you would have a hard time telling them apart better than guessing. As long as the amp is considered neutral or transparent with a SINAD in the middle 90's up good luck picking which is which in a blind test.

Preference of sound is not the point. Whether one thinks certain products that reproduce music or if a live event sounds "good" is subjective. If one thinks amp A sounds better than amp B buy amp A but If an amplifiers noise and distortion are measured to be beyond human hearing then that component is considered neutral or transparent, it neither adds or subtracts from the signal sent. If 2 amplifiers measure the same and are considered transparent then they will sound the same or so close they can't be differentiated in a blind test. The test can be one day or 2 days or 10 days, months apart. If one can successfully pick one over the other better than chance no matter how many times they listen then the amps either don't measure the same or the test is flawed.