1. Drive the Limited and SRT and see if the SRT stiffer ride is something you can live with.
2. If the car has a NAV radio, make sure the CDs are included. Over $200 to replace.
3. Ask about the luggage that came with the car. That will cost you $300+/- to get from a private party. (600+ from the manufacturer) SRT versions are even more expensive.
4. Make sure the tires have lots of life left in them. Or have the seller buy new ones. Major expense there.
5. Check maintence records and the FSS to make sure the oil changes were done. If it's near the next one, have the seller change the oil & filter. ($130+/-)

I'm sure I'll think of more...