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You're best bet is the Swift Spec-R, they are one of the few springs that actually increase spring rate and lower the car...its going to be more for looks at this point though as to get an actual advantage you'll need MUCH higher spring rates.
IMHO, when lowered on drop springs with large drops (more than 1"), there isn't enough bump travel on hard corners with the spring rates drop springs provide.
I run the 2008 Nismo springs, does not lower the car (which I prefer) and has stiffer spring rates that work very well at the track. You can look for a used set or order them new from a Nissan dealer.