The Kappas are nice, you'll like 'em. Even the Reference's are good in that size - I bought my son a pair for his Ford truck and the midbass on them is impressive.
I've always had a soft spot for the styling of the Marquis/Crown Vic. Nice cars. Good luck with it.
1999 Buick Park Ave Ultra
Head Unit: JVC KWHDR720
EQ: Audiocontrol EQL
Front Stage: Hybrid Audio Technologies Imagine 5.25 mids, Morel Maximo tweets
Sub Stage: Boston G3 10", 0.5 cu ft sealed
Amp: PPI Phantom 900.4
Rear Fill: Boston SE953 6X9's