^This.
Based on your description of just wanting to lower it a little and being cost conscious, take a look at this option: http://forums.hybridz.org/topic/117631-new-s30-shock-and-spring-option/
The second page shows a before and after ride height shots on a 240.
These are very well priced. You can get Stagg springs and Vogtland shocks for $294: http://brandcarparts.com/catalogsearch/result/index/?dir=desc&order=price&q=260z
I don't know of a better priced option for all four corners. There's more involved, though, than just replacing shocks and springs. You should also be checking all bushings, ball joints, tie rod ends, sway bar end links, etc. These things can add up quick.