If using the struts in the meantime, before getting the coilovers, I would recommend using the swaybar. The 18mm bar, not the 24mm SS bar. Autocrossing, running stock springs and struts in the rear, I had massive body roll, oversteer and understeer. Unpredictable and trying to turn around backwards you every chance it got.
Ended up using the base model Cobalt swaybar and stiffer front springs. It's now a completely different animal to drive, in a good way. Predictable, and able to catch it when the rear end steps out.
I say try it and see what you think. You can always remove or install one sides endlink to try the difference with or without it, in a safe test area.
Swaybar install and removal on the car is easy. It does require the removal of the muffler.