try a 'search'. Eibach is often recommended, and i think most of the 'sport' alfa options are Eibach!
bear in mind, to do it properly, you should also upgrade the dampers, especially if they've travelled a lot of miles (>50K) meaning they'll be becoming worn.
for value, the 'Eibach Pro System' springs+dampers combo is worth considering (presuming it's available for your car). otherwise, mix and match, say springs from Eibach, H&R (lower, harder), Novitc, KONI, with dampers like KONI Sport, KONI FSD, or Bilstein B6.
next level up are premium coilovers.
there's HEAPS of discussion about suspension in the forums. then just look up the respective websites for each manufacturer for availability. easy.