My car won’t be used on the track ever, but I do have some pretty poor roads in Sydney ! So I feel the bumps and humps a lot
In my humble opinion, save your $ and don't upgrade. Even the road springs are stiffer than any of the aftermarket shocks. The 4C will never be a crappy road car, regardless if you put $2k or $10k worth of shocks in it. Plus you need adjustable end-links at the minimum or full adjustable swaybars with any new shock system. It simply isn't worth the cash flow if it will never see a track.
Chris Harris just had a nice piece on the latest Top Gear Episode comparing the new Focus ST and a Lambo Aventador on British B roads. As we can all guess his conclusion, for 90% of the roads, a high horse powered sports car is overkill and sucks most of the time. Something cheap, good enough suspension (designed for road), and good enough power, will be far more enjoyable than the Lambo most (if not all) of the time.