I personal opinion on Myvi is....
They have very clear highs and mids....
The LOW boom boom is NOT even there...
So adding a sub first is a wiser choice than changing to ANOTHER coaxial speaker... I don't see a point here...
If i were you, IF I want to change the front speaker to make it sound better, I'll save up and get a 6.5" Component straight up... No second thoughts...

Again...
That's only my thoughts...

I didn't say anything about budget.
I was just saying, IF I WERE HIM, I would not change the Coaxial cause it won't make much difference.

Adding a Sub, no matter active or passive, would make a bigger difference.

AGAIN, that's only my thoughts

1 cent opinion.

Cheers

Well, that's for IF and ONLY IF he wants to mah... hehehe
Save up = Save up time and money

LOL

Cheers