Alot depends on how much you want to lower it and what kinda ride you're looking for after.
If you wanna lower it and fit different wheels purely for cosmetics then that can be dealt with in a different way to if you want a lower centre of gravity and a stiffer, sharper ride.
Another thing to bear in mind is who will fit it for you?
If you're looking for cosmetics / wheels the final ride height is ultimately what you want to fine tune - I'd recommend ride height adjustable coil overs so you can fine tune the height to avoid scrubbing etc but give you some level of flexibility.
If it's more to improve the handling the ride height isn't as important and you can get damper adjustable coil overs, again giving you control over how firm the ride is. Or just a plain damper adjustable kit ...
Alot of these fixed kits you can buy have such varying results - it might be to soft or not low enough for your taste - and you'll not know till you've spent the time and money fitting it!
You could go as far as buying a kit that can adjust both - but they're serious money for anything worth having.
Hope this helps ....
(As for the phrase 'coilover' it just mean that the coil or spring is set above the shock - when people refer to coil overs what they actually mean is ride height adjustable coil overs, as this arrangement has to be used to give the adjustment. If you bought a plain and simple coilover setup you wouldn't automatically set this height adjustment)
Sorry to be pedantic Gibby - just thought I'd set you straight
