You have neglected to have the mb quart 3 way system purpose built for the e90/1/2/3 priced at £430. This is what is going in my car along with the pioneer 80prs.
Amp quality is important I am going with genesis in my application.
My car installer highly recommend audison and hertz amps. The 5 channel audison hp5 is tiny in footprint and very meaty in power and would power mids and tweets with two channels, underseats
With the other two and still have 700wrms left for a sub in the boot. It also fits nicely in boot side where cd changer normally lives.
E90 330i SE Auto Graphite Grey Metalic