Cost heavily depends on if you and the fiance can do it yourself or if you are going to have someone else do it.
Coilovers are badass, I have Megan's and they are awesome. Totally adjustable ride height and dampening. But yeah, they cost more, a lot more up front, actually. You can get them for around 900, probably 850 if you sweet talk a vendor, like I did. :ninja:
Springs work great too, but they are a little harder to install. Not THAT much harder, but a little more dangerous. Much cheaper though. 100-250ish in price, install would probably cost a little more, but only by 100-200 bucks, tops.
I did my coilovers myself with my friend and his dad. Was like 30-45 minutes per corner + lots of breaks and BSing. My ride quality is awesome, and my weight is adjustable for winter, which is really important being in MN.
Depends on your budget, a lot of people (including me), will say if you can afford coilovers, get them, but if you can't afford or just don't want to spend that much money, get the springs.