why not use linear rate race springs, like trd coils, and chop them down to your own preference? (using shorter shocks to keep them captive/legal) just dont go too nutty with the angle grinder otherwise you will run out of shock travel and you will have issues with roll centre in regard to the front control arms, which you will if you go to low regardless of what sort of setup you are using be it adj. coilovers or progressive rate lowered springs
if your going to go to the effort then its worth looking into converting to short stroke front shocks, you will lose at least an inch in ride height (25mm-40mm depending on shocks) before you wind down your adj. platforms or chop coils, the real advantage though is that the shock works better with the shorter spring, there is a very good write up on
club4ag.com
if you have no intention of moding your car for serious performance, you just want it to sit a lot closer to the ground and get rid of most of the gap between the tyre and the guard then dont dismiss the jamex progressive rates, for the money they do a pretty good job and they dont look half bad, a mate has them fitted to his car and it looks the business, he is however last i heard planning to ditch them and use trd race springs not because the jamex's aren't alright but because like the rest of the car things are getting a bit more serious, gap between the guard is about an inch with 14's and the car sits low but legal, speedbumps and driveways are not a problem