You want to get the 150 hz model (they call it the "brown" wired model)...it is a 250uF cap for those of you who want to buy the equivalent directly from an electronics parts outlet. Also, make sure you get a non-polarized capacitor if you go that route. The Amazon.com caps are of the correct type:
http://www.amazon.com/gp/search/ref=...0&Go.y=0&Go=Go


Here is the Crutchfield link to the correct model bass blocker. I am unsure why the previous link I posted didn't work, but I am going to try it again.
http://www.crutchfield.com/S-vOKvTf1...h=bass+blocker