Its a matter of personal preference, do you like the ride height/handling of your car as it is now? Also how many miles on it? If you get the sport/lowering kit, I think you'll find the ride to be harsher but the trade-off is that handling will improve. If it were me, I'd go with the FSDs/stock Aero springs. I've done this set-up on a number of customers cars and have gotten lots of good feedback, sure the price is high, but in the end I think its worth it if you drive the car a lot/plan on keeping it. My rear shocks on the wagon are just about toast after 80k, so I'm plan to install this set-up in the next couple of weeks.
1997 Saab 900 SE Convertible "That Yellow Bastard"
2004 Saab 9-5 Aero SportWagon "Mr. White-1"