1st off.....if your amp's or headunit's built in crossovers can handle highpassing the four 6.5s and lowpassing the sub, then I wouldn't worry about getting an external crossover. The less things in the signal chain, the better //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif So that's what you need to decide first. 2nd of all, an EQ isn't a fix-it-all, it is the "icing on the cake" to a stereo. Work on speaker positioning, phasing, sound deadening, killing reflections, level matching, finding the right crossover points, and other areas of the install before worrying about an EQ. Then, after you get the install set up properly should you worry about an EQ if the sound is still not quite right. Putting an EQ in a unproperly setup install is like putting a bandaid on a gunshot wound.......not very effective //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif So, if you have all of the above figured out and set up appropriately, you need to decide if you need a parametric EQ (smaller # of bands, and adjustable freq) or a graphic EQ (usually higher # of bands, frequencies are fixed).