Height Drop
In ombination with 18" i'd certainly recommend it. Of you go for just the springs you might end up really disliking the new ride quality of your car. Also if they're heavy 18" 's you need to upgrade your struts anyway (stock will be broken in no time), so you might as well spend a bit more on coilovers.
1995 noble green MX-3 RS (sold)
1994 clear white MX-3 GS (r.i.p.)
1987 white RX-7 FC
1993 mighty grey MX-3 GS
1994 clear white MX-3 GS (r.i.p.)
1987 white RX-7 FC
1993 mighty grey MX-3 GS