What to look for when buying an EQ

Wade, as has been said, an EQ and a Xover do two entirely different things.  Your post indicates you are trying to adjust the sound with a Xover.  It ain't gonna happen.

A Xover simply divides and splits a signal based on the frequency and sends different bands to different outputs.  It is used to send the subwoofer frequencies to the sub, the mid frequencies to the mid and the high frequencies to the tweeter.  Once it is set, it is set.  The main use for a Xover is to protect higher-frequency speakers from trying to play too low frequencies (and thus damaging them.)

An Equalizer is simply a sophisticated tone control.  It does the same thing as the bass and treble controls in your head unit, only it has several bands of adjustment rather than just two or three.  An EQ is a very powerful tool and they are often misused by people who do not really understand them.  The main use for an EQ is to cut peaks and boost dips in the system frequency response, but it cannot compensate for inadequate speakers or poor installation.

ALL systems that use more than one speaker per channel use a crossover of some type.  Some systems can benefit from the proper use of EQ to compensate for system problems.  In properly designed systems, both tools are set-once and forgotten.

A crossover will not give you "crisper highs" as it has nothing to do with adjusting the signal.  An EQ might allow you to boost the highs, but it will add noise and can cause other issues.  The best bet for getting "crisper highs" is to change out your tweeters with "crisper" ones.