Cadillac makes a sport sedan known as the CTS. 4 doors, RWD, standard 3.6L direct injection V6 making around 300HP/TQ. Cadillac's performance brand is the V line. CTS-V, XLR-V, etc. The CTS-V used to use the LS6 and LS2 engines (both 400HP/TQ). They were VERY fast, and handled pretty damn well for an almost 4000lb sedan. Also had all the little luxury bits that come with a high-class car. All the mods for the LS6 and LS2 worked on the CTS-V with no issue.
The new CTS-Vs use a supercharged 6.2L engine (LSA) that makes around 550HP. Very fast, very nice. Google CTS-V and take a look at the pictures/info available. The new ones are really, really slick. Kind of expensive to buy new though.
1993 Mustang GT - Sloppy Horse - SOLD
1994 Mustang GT - Dedicated Racear - Full MM catalog with 03 Cobra IRS - Codename: Rigid horse