Hey there, welcome to the forums.
Good choice on the 189 style rims. Great style. What I have on mine right now. I think you will need 15mm spacers to have the rears fit properly.
Suspensions I don't have much experience with.
In my opinion the most cost effective mods for a 328 are cosmetic.
I would recommend a CSL style trunk, and fitting LCI tail lights. A roof spoiler might also be a very inexpensive mod if you are interested.
Good luck with your search.
Ps, I might be interested in off-loading my 6-month-old 189s and getting M6 reps. I live in chapel hill, so maybe if you were interested we can do a local trade some time down the road. =)
2006 E53 X5 3.0i [Gone]
2008 E90 328xi [Gone]
2011 E92 LCI 328i [Gone]
2014 E84 X1 35i