Thanks all for further help and this is roughly what I am thinking at the moment for my 2012 BMW 328i.
I am planning to keep this car for 3-5 years (hopefully), so I will utilize this spend for sure.
M3 Body kit (original or shj one, will decide upon the price and if its allowed).
Add high bass woofer with additional amp at the back, as music system is awesome but lacks the low level bass.
May be upgrade two of the main speaker after the woofer add-on is not enough.
Add free flow K&N drop-in filter.
Borla exhaust - touring one (not loud).