have at look at engines, bhp if thats your thing. 320 is just under 200bhp, then 330i 230bhpish, then 340i is a 6 cylinder with around 320bhp. get m performance/shadow trim, so it looks sportier, bigger wheels etc. can get any apart from 340i in xdrive (4 wheel drive), but suspension is higher as a result and I can see the difference.
Or go for M3 like I did, nice 440bhp
. Rear fender, flared wheel arches make it look incredible, real presence to it and sounds immense. Right balance between aggressive, sporty etc without look like something from FastnFurious like a lot of jap performance cars do.
or get audi a4/a5 equivalent, with sline trims. their 4 wheel drive system better than bmw's. or s4/s5 if you want to get into 300bhp territory, 6 cylinder engines.