So the Higher the LP filter the more it blocks the Highs??

more specifically, lets say you set your LPF at 70Hz (that's about what I aim for) on your amp.  If you use sub specific pre-out from your deck than it'll send the amp somewhere around 10-300hz to the sub.  That means that from 10-70 Hz your sub will get full power, above 70 Hz will get power but at a -24v rating.  This means you will still hear the above 70hz sound just very softly.  If you want to lower the higher frequency sound more you can install an additional crossover witch will lower it another 24 volts, making anything above 70Hz -48 volts.... provided you set your additional crossover to 70Hz.

so to answer your question, NO the higher the LPF the more highs it lets in.

correct me if i'm wrong, but the HPF works opposite to that.  The lower you set it the more highs it lets in, and cuts the lows by -24 volts.... I have WAY more experience working with low hertz systems.  LOVE DAT BASS!!!