Hi I know this is an old thread but I have some things to contribute. While I definitely suggest a power capacitor to keep your voltage from dipping and your car maybe losing power when you need your traction and ABS to work most, I actually have done this upgrade.
*The limo 215 amp alternator is an exact fit to the base sedan.*
I have a 2006 (so a 2007 and up would also work) Non-Performance DTS Luxury II and both my alternator and battery went bad and needed to be replaced-- seemingly at once but I'm sure it was a case of one going bad and causing the other to fail. The battery was only 2 years old. Anyway I bought the limo version and while it was slightly larger in appearance (with heftier cooling fins and a little more copper inside), the bolt pattern was exact. It was a long, 10 hour job for the mechanics that hadn't worked on it before to take the bumper off, the radiator, oil level sensor, etc. so it was worth it to try to see if I could upgrade it since I'm going to be putting in a nice stereo with 2 15" Kicker square L7s. But definitely try just using at least a 2 farad power capacitor (with a circuit breaker) for your 1000W of power before getting into this job. Luckily, the shop's computer quoted the job at only 2 hours and that's what they billed me, instead of the 10 hours. =) I bought the limo alternator for about $70 plus core, and rockauto accepted the bad non-limo alternator as the core I returned. Gotta love it! I previously had my Grand Am's alternator upgraded from 150A to 210A because the headlights dimmed on bass hits but the alternator just made the headlights brighter yet still dimmed, until I bought a power cap.