I can't believe you will be able to notice the difference between 25 or 30 mm. If you're looking for an ugrade of your frame, you should choose H&R or Grams springs or better Bilstein and BC coilovers; instead if you would a very low car, you could buy some cheap coilover kit like AP and install them with the rings unscrew to the maximum possible.
Mainly cosmetic mods on my blue one, although I've put twin exit exhaust on it too. Building the megane powered one too though that's a lot more mechanical work