I hear you about the passion and you're right about the tweaking options. The more options some people have, the more likely they may never be happy because they will alsways be tweaking. For me though, it's the opposite. The less options I have the more frustrated I get when I do not have the option to fix it with something like a DSP. Case in point is my Fords factory radio. I learned my lesson and I now get the good quality stuff first with the bells and whistles so I always have the option to upgrade without buying all new equipment because I tried to save $150 at first.
Don't sweat the options on the DSP. Download the App and play around with it for a week. It's going to take time to learn. Test ride the TwK 88 software too and you might find its basic function easy to use. You can still run a two way speaker set with passive crossover with the DSR1 or JL TwK because they both have a basic function to keep things simple and you would still have some left, right, and sub time alignment control just like you would with the DQ61 with basic EQ. You could use that setup and be perfectly happy with it or as you read more and educate yourself to the point where you have more confidence than you can remove that component sets passive crossover and try active. The point is it can be as simple as the DQ61 or a full out high power 3-way with subwoofer setup such as Jeff is showing. The manufactures of these DSP's are making them fit everyone's skill level so they can sell more of them, which is smart.
I would recommend you do not use that PPI amplifiers crossovers to run an active setup. It would be very difficult to do without an RTA and you could easily blow a tweeter with one wrong move if you don't know what you are doing. I have to say I haven't tried that myself but I know enough about these to not recommend that route. The PPI amp itself however I'm sure is a perfectly fine amplifier to use with a DSP or aftermarket HU.
Your fear about the highs being too bright can easily be fixed with any of these DSP's. many passive crossovers also have tweeter attenuation just for that purpose to tame them if the customer wants. The DSP is really about the best tool to come out in car audio in a long time. I absolutely love mine.
Generally speaking it's best to cross over with a two way as low as you can with the tweeter you have. The rule of thumb is to cross over about two times the fs of the tweeter when using a steeper slope such as 18 through 24 db per octave. The better and larger the tweeter is, generally means it can be crossed lower. For example that NVX X series set has a crossover point of 1500 hertz with the passive set. No that is not a typo and you can go to NVX site yourself and download the manual to see for yourself. I have the SB Acoustics version of those NVX tweeters crossed over at 2400 hertz @ 24 db LR right now with Focal Woofers and it sounds really good. In my truck I have my tweeters crossed over at 2600 hertz @ 24 db LR because that is about as low as the Tang Bang tweeters can go before it doesn't sound as good. I have a passive set in my CX5 with the DQ61 and that I think is about 4000 hertz @ 12 db per octave. This is where I plan to replace with the NVX or SB Acoustics set.
I like to have a low crossover point because it brings the sound stage up high on your dashboard and keeps the door woofers in the frequency range that they play best. Larger woofers suffer from something called beaming, which you can google to learn about. The larger your mid woofer is the lower the point at which the mid woofer starts beaming higher frequencies.
This is where a three way speaker system has an advantage because you can cross over the woofer under 1000 hertz, the mid range around 4000 to 8000 hertz, and the tweeter 4000 to 8000 hertz and like Jeff pointed out, you can put the smaller midrange and tweeter up higher closer to your ear level. Three way active setups are something I havent ventured into yet as they are complicated and expensive to build. Great sound quality though can be had with a properly set up two way with a subwoofer. The subwoofer is key in any sound system and I could not imagine any system without one. I don't care how good you think your 6.5' mid woofers bass is they will never play 20-50 hertz like a large subwoofer can.
Some good reads for you to learn more:
http://www.audiocontrol.com/downloads/tech-papers/tech-paper-102.pdf
https://www.sounddeadenershowdown.com For proper sound deadening
Speaker beaming tables
frequency tables
Car Audio Fabrication - Custom Techniques , Video Tutorials Car Audio And
https://m.youtube.com/user/CarAudioFabrication
