My 330ci on stock sport suspension ride about the same as my old A4 on H&Rs/Bilsteins. So I would imagine the 330 sport suspension would be a good upgrade for you.
If you don't want to lower your car, I'd keep an eye on the classifieds for ZSP, ZHP, or maybe even M3 suspension parts.
Summer: BMW 135i M-Sport
Winter: 2004 Audi A4 Ultrasport 2.7tt
Year round: 6 cylinders, two turbos, and 6 speeds.