The Klipsch Promedia sub has speaker amplification built in and so no telling where the crossover on it is set. I'm sure it's fixed pretty high since those Promedia speakers have tiny drivers. Normally, you want to set the the sub crossover to where the speakers start to roll off in bass response.
Well, unless you have passive speakers and a receiver with active bass management. Then you can choose a higher crossover point. However, there are some subs that have RCA inputs and outputs, so you can chain the sub in between the audio source and the powered speakers. And then a few of those I have seen, such as the SVS Sound compact subs
, have an 80hz high and low pass filter so that the crossover is fixed there at a reasonably high setting. On most subs, the crossover only affects the sub output.