Hi there, me too is on the current Myvi variant & you may consider by adding a pair of good quality tweeters (only) to the front (plus some secret recipes to enrich & enhance the effect out of it!) to match with your stock speakers! Balance money will go to the soundproofing since you mentioned that you would liked to minimize the exterior sound intrusion.

FYI, me is running the suggested above setup minus the soundproofing & this is just my humble opinion for you

yes, mine has done the suggested addon(s) in my myvi on stock speakers front & rear, without soundproofing the doors due I don't need it
...will pm you on the rest