It would be worth it. When I had the 3 way on the 80prs my 450/4 ran the mid and tweeter with its CO. If I needed to move the tweeter the mid went with it. I got it down to a narrow bandwidth of annoyance. Drove me nuts.
Harmon said it don't matter. At least in my case it didn't matter. You have to get into the 200s to start noticing direction. Maybe it's the way the EQ sets up idk. The MS-8 has its algorithm and it works, way above my head for whatever it does. Maybe I just got lucky with the install.
Ohhh well, you probably don't need to have LPF for the mid to be at 4k anyway. Cross it lower, see what happens. OR cross it at a higher slope. Not sure what 80PRS has as settings, I can do 48db and probably steeper. Crossing at 12db at the same x-over point would give you too much "warmth" as you end up having multiple drivers playing same frequencies.
Maybe just that line. I brought mine down to 3k -24
Then bring your mid up to over 120. That's why it's muddy.
Xovers don't change the on/off axis response and if you turn off the tweeters it would shift to the right to an extent depending on how low you're crossing the tweeters at. If you cross your tweeters too low than you can definitely damage them.
I wouldn't use the supplied mic and auto tune feature on the 80prs, it doesn't do a very good job at all and I've tried the auto-tune on the 80prs, 800prs, and 99rs, all which i've owned.
TA'ing the sub does make a pretty big difference with blending it to your midbass. If you don't have TA abilities, just reverse the phase on it and see how you like it.
Sub is definitely not the most important thing to time align but it does seem to help.
Usually a decent starting point would be your mids around 63-80hz with a 24db slope depending on how low they can play to around 3khz-3.5khz. Tweeters 3khz up and also 24db slope. Try not to overlap them so much with the shallow slopes.
