B5.5 estate lowering: springs or coil overs?

[VRB321]

I have a 2004 Passat estate 5 speed auto. I recently changed the 15 inch se alloys to 17 Monte Carlos and now looking to lower car by about 30mm as I still carry weight in the back. As standard the cars seems to have a larger gap at the front arches compared to the rear arches, is this normal? My aim is to have it look an even clearance all round. Will springs do this alone or do I need to use coilovers to achieve this? Please advise me?which product?as I'm a complete novice and also please recommend any brands? Many thanks