Just a friendly reminder, these cars can only use coilover on the front suspension. The rear suspension is a multi link design, with the springs and dampers in different locations. So all you're getting with a "coilover" kit is 2 actual coilover units for front, shorter/stiffer springs on adjustable ride height perches, and adjustable dampers for the rear.
IOW, if you're happy with the ride height and spring rate as it is like me, just change the dampers with parts that actually do something.
And BTW, arguably the best coilover kit is the Mazdaspeed accessory items. They're built by KW, based on the V3, but the spring rates etc. are specified by Mazdaspeed.
If you want to lower it any more than stock, these are the only way to go for sure, IMO. You also have the advantage of much better, and very adjustable dampers, for fine tuning.
Anyway, what I would never, ever do is just swap the springs out to lower it and use the stock dampers. Big mistake, the stock dampers can't even keep up with the stock springs, particularly in the back.
IMO, stock springs, with high quality dampers and tires, and a stronger rear sway bar, will improve both ride and handling quite a bit, for considerably less cost than any coilover. But if you want the best option for lowering and ultimate handling, just pony up for the Mazdaspeed kit. AND a stonger rear sway bar. You get what you pay for, pretty much always.
And don't forget about the tires. The stocker's aren't too bad, but there are better options that cost less and do everything better. Fortunately or unfortunately, depending on your perspective, I trashed the stock tires in 7500 miles, without abusing the car at all.
