BMI Whale vs King Cobra V2, others?

I would follow DKuipers advice and get a trail listen to Shunyata Hydra, which improves all components in your system, before you spend big money on individual AC cords.
You can call Galen Carol in texas for low down on the hydra.

I know I'm compromising potential sales here folks, but my honest opinion is this--ditch all the aftermarket powercords--all of them, and plug stock cords into the Shunyata Hydra line conditioner. Simply amazing. I sell three different brands of aftermarket power cords, but the truth is brutal: a single Hydra makes all of the cords moot. YMMV of course.

Haven't tried the BMI, but I have a KCv2, a Viper V2 and a Black Mamba. The KC is on my CDP, the Viper on the pre, and the Mamba is on the Power amp. After swaping cords around from component to component (over several months) I can honestly say that I cannot bear to listen to my system without the KCv2 on the CDP. It makes a BIG difference. I won't go into superlatives. ...Just listen. While good, the Black Mamba and Viper V2 just don't bring the sound to the same place when attached to my CDP. Great were they are though.