Seems like if it was neccessary, the suspension parts manufacturers would include the shocks with the kit. A basic kit is just springs, more expensive kits have them. so, I guess, it's just a matter of preference or whether or not you have the cash. When in doubt, ask the manufacturer. They should know. However, they might just tell you it would be a good idea just to get your money. :nonono: You could just do the springs and see how it rides. If you don't like it, get the shocks.
I'm getting ready myself to put springs on my 2013 SEL in a couple weeks or so. I'll post my results.
Good luck.