Nothing wrong with that, you want your regular speakers frequency range to start where the subs stop at so you maintain the full sound range, as for your deck, basically built in is the eq and h bass, hbass involves the rear speakers that adjusts the frequency for those, you may have that off those, otherwise your only option is turning down the eq and adjusting the amp as needed without overworking the subs or the amp.....
other then that your only options are what everyone has already suggested external eq is a pain to install if you having worked on it much, and how much you spend usually always defines how good a unit you get

 

Yeah, I never have the H-bass turned on unless my subs are all the way down or I want to give the alternator a break. I suppose I will have to buy some crossovers. At Best Buy they had some fequency limiters (i think thats what they were) that limited or something the freq to 2000mhz. 2 for $11.99.

 

a lot of the crossovers that are better to have are usually with component speaker sets but good ones are rarely cheap but you will be cutting off the bass for sure if its at 2000z lol