Great write up and congrats!
I dont think anyone has been happy straight away with an MS-8. I spent weeks trying to get the right tune. But it will be worth it.
I'd try changing the xovers to 200hz @ 24db/octave for all your speakers, and a 40hz 24db subsonic.
Also have a play around with calibration volume, it makes a huge difference. Even 2db can affect the sound quality. Try lower and higher volumes and note your impressions. Im thinking because your speakers are very sensitive, try lower, so -30db. I have found -20db works for me but yours will most certainly be different as you have a different set up.
Good luck and hope you enjoy tweaking!
2008 E92 335D SE
2010 E90 320D SE
1994 E36 318I SE
1996 E36 316I SE