Sways, convert to FE4 setup with ZL1 sways if keeping staggered wheels.That is cheapest route and should be very good.Do Hotchkis drop springs for 1" drop and best ride and good handling if lowering, also has good clearances with only 1" drop. If you have $$ do coilovers for best ride and handling, but not needed really unless serious about tracking the car.
See what I have in my sig? Thats overkill for canyon carving as to the sways but wanted adjustabillity if needed as I auto x the car alot and get rid of understeer so you arent manhandling 2 tons around corners. Biggest thing to have on the sways is that they give you closer to neutral steer and get rid of body roll, this makes the car more fun as you arent fighting the massive understeer you have now.
#1 car 2010 Black 2LTRS 1/28/10-10/15/11, 17900 miles
#2 car 2012 Red 2SSRS 10/15/11-
Mods: Outlaw Axelback & J Pipes/Heritage&Stillen Grill/Halltech CAI/Apex Scoop,Washer Bottle/OEM Strut Tower Brace/VMax T/B/ G.M. Blade Spoiler/SLP Splitter/TSW Nurburgring wheels & Michelin Super Sport tires/JBA Shorty Headers,HiFlow cats & tune/Remote Clutch resovoir/ Pedders Supercar coilovers and Pedders 27mm/32mm ZL1 Spec sway bars / Whiteline craddle Inserts & Upper rear arm bushes/ 416/414 RW HP/TQ