I doubt a spoiler will have much effect on aero. It looks like the 2000 SL1 and SL2 have the same CD of .32. I think the only major difference (exterior) between them is a spoiler, fog lights, and alloy wheels. Maybe an aftermarket flush/lip spoiler would be more effective, though I doubt it would be cost effective. My 1997 SC1 on the other hand, would benefit from an SC2 spoiler (SC1/.33 - SC2/.31).
I do have Vortekz brand vortex generators and smooth (full moon) hubcaps. I think I have $25 shipped (plus paint) into the VG's and $35 shipped into the hubcaps. There are pics in my garage.
www.manufacturersdepot.com Browse By Manufacturer:Vortekz Category
cripedistributing.com : 14" Stainless Hubcaps 81130-41 (4 pieces) [81130.41] - $18.00