I have another minute so I'm going to try to help you make sense of the REW EQ box I marked up.
In blue, the treble and bass can be adjusted to match your preferences. This can include full-blown house curves, like a harman curve or a line on the equal loudness countours. Simply put, the rise or cut can start on any selected frequency. My desktop nearfield monitors have -1.5dB/octave starting at 1500hz, and a 3dB/octave rise starting at 150hz. I have it set up where I can turn those boosts off easily, because I set up a "flat" EQ and a "boosted" profile. That's for another time.
The red section is where all of the sacrifices happen for on-axis response. In a passive speaker, the amplifier sends full power for each frequency to the crossover, which divides the energy across each driver. These components dissipate extra energy as heat, which allows them to play more accurately each frequency they are asked to. This is different from DSP, which tells the amplifier to do less or more per frequency. This is important as it will change the instructinos your amplifier is given, unlike passives. Understanding this difference is key to utilizing DSP to it's fullest extent.
As I suggested in the photo, every three decibels of gain increases the wattage by approximately double. The reality is more complicated, as are logarithms, but we'll stick with the easy explanation. This means changing the "sensitivity" of the speaker to allow more room for corrections by changing the
Target Level. If the mic calibrations are correct, 72dB takes only a few hundred miliwatts from an 85dB sensitivity tower. Bringing that sensitivity down 3dB requires so little extra power when bringing volumes back up to listening levels, only another 100mW or so. The best advantage of our new amps is having a whole 500 or so watts available, which makes the issue of trading lower sensitivity for accuracy trivial. Any driver that is also brought down this way has had it's power handling superficially increased. There will be less power flowing at those frequencies. Likewise, any driver that is boosted or stays the same receives the full brunt of the amplifier power. Since your speakers are ported, I would always test them with a high-pass filter on the miniDSP (where you do the crossover now) around 45hz to protect the woofers. Porting is fascinating, and I recommend learning about it. Pushing speakers below their port tuning can damage them, as they are in their greatest physical extension. You could also easily lower the subwoofer crossover to 60-80hz. The specs of the tower justify that. And that subwoofer is measuring incredibly well up to 80hz.
In purple are the peak settings. An EQ "Peak" can be up or down, positive or negative. The width is the "Q", inverted for your convenience with smaller numbers making wider bigger peaks. "Gain" is up or down, increasing or decreasing volume. In REW, they are calling this "Boost". What REW is asking you is "how much do you want to push your amplifier, bro?" I am no amplification expert, but if you have 6dB of gain on a filter (pretend one of your eq peaks is inverted, raising the volume of a frequency band) it will demand four times more power from the amplifier than if the gain were 0, while the amplifier is playing those notes, or frequencies.
Here is my EQ on my monitors currently. Not the same software, but the same idea. Note the gain in the bass. I would demand a lot from my amplifier to run like this, and I would likely cross the line level threshold (in your case, 4V) and cause an amplifier shutdown. Note the global gain of 0dB.
Here, I have lowered the global gain (also known as preamp volume, preline vol, etc.) to never pass above 0dB. On the MiniDSP, this is "Gain (dB)" as I circled above. This lowers the sensitivity of my speakers considerably, but extends their range. I can't play the speakers as loudly this way, as the small diameter woofer is always going to have a maximum SPL of about 86dB down at 50hz. I am simply lowering the volume of the rest of the speaker to meet the weak link. If I were to use a subwoofer on this setup, there wouldn't be a boost down low. No negative global gain, no volume limited by bass output.
To relate this back to our REW settings, you can select the range you would like to correct with the
Match Range section. If I were setting up a set of mains for a subwoofer, I would pick something like 80hz to 20000hz. Then to set up the sub, I might say 0hz (or whatever is the lowest) to 80hz when adjusting the subwoofer. When designing speakers, you can choose ranges like 1.2khz to 20khz for a tweeter, for example.
Individual Max Boost is how much you are willing to have a single band of EQ boost a range. There are negatives to overboosting certain frequencies, but you can safely put this as high as you want.
Overall Max Boost is important because multiple peaks can come together to create a larger "overall boost" at a certain frequency. In the case of my monitors, this is 8dB, as I am willing to apply -8dB of gain to my speakers to prevent damage. On the miniDSP, this is the "
Gain (dB)" setting I circled in red before. Flatness Target is how accurate you would like the speaker to be. Most speakers are judged as good when they are flat to 3dB (+/-). Though lower is better, I guess. It depends on how many bands the new MiniDSP's let you have.
You may notice some peaks and dips that don't change no matter how much EQ you throw at them. These are the room and the listening position in the room. Any EQ related to these can be safely ignored. Sometimes a speaker will reveal quirks and resonances when pushed at certain frequencies. Isolating these issues can be difficult.
I think this is the best I'm going to be able to do for the next few days. I'm sure someone else can help you whlie I'm away. This is a really fun time to get into projects like this and I'm sure you'll be satisfied with the results. There are many more qualified than me who can help you over the weekend if you choose to ask. Good luck!