makvli, KSports are a great product, you'd love them.
amair, all I've seen people have lowered easily and inch, past that and some people have gotten rubs.
And coil overs could mean 2 things.
1) Replace the stock sprint and go over the strut
2) Complete strut and coil over assembly (1 unit)
The advantage of #1 is that like you said they are adjustable, this is from ride quality, height, and cornering for autox, fast mountain roads, etc.
The advantage of #2 is, also #1, but the struts themselves are also usually adjustable, this allows you to fine tune you suspension for ride comfort and cornering ability.