Keep in mind that with the 4-link kit you also need to buy coilovers. Those will likely run you $350-500 as well, so your 4-link could be twice the price.
That's what I was about to mention as well, but the ad says they're included. I've been trying to decide between a four link & springs too and thats the best price I've seen.
Make sure you're looking at the right springs though. The model number you listed was for a 3100, they won't fit your 3600.
