What I want to do is hook the speaker outs from my amp to my computer with some adapter to see exactly what frequencies are present between the crossover points. This way I won't have to guess where 2500hz is on a lpf/hpf knob that is only labeled with 500 and 5000hz. I want to visually see the range on a db/hz plot. Is there a program like I described above? What's the name of it?

Is there a device that will accept the + and - speaker wire and convert them to a stereo connection for the mic input on my computer? Would this just be a regular adapter that connects the - to one lead and the + to the other lead of the stereo connection?

This is to help get starting points my fronts. If it works well enough, I may just use it to fully tune it unless there are convincing arguments against it.

One thing you can do is take a 5~10w resistor (make sure it's not inductive), hook it up to the amp, and measure the voltage drop on the resistor while playing the tone you want to set the crossover to.

For instance if it's a hpf and you want to set it to 1khz, start from the lowest setting while playing the 1khz tone and when you see a drop in voltage across the resistor, then you know you set the crossover close to 1khz. This is purely based on logic, so if there is a flaw in this method, please point it out.

Though in my opinion the thing to do is play with them and set them where they work best for your ears.