Here is XS-500 Escalade
Supercharged w/6.5psi boost
522hp at the flywheel. 0-60 in 6.6sec.
costs $20k comes with 4yr/50,000 mi warranty (dealer installed).
link (http://www.motortrend.com/features/performance/112_0206_superesc/index1.html)

GM's own twinturbo Escalade
580hp and 580lbft of torque. enough said
link1 (http://www.edmunds.com/news/autoshows/articles/48020/page006.html)

SVC supercharged Escalade
supercharged w/4.5psi boost
500hp with 535lbft of torque. under 7sec 0-60 time.
link (http://www.motortrend.com/features/performance/112_0109_escalad/)

add more aftermarket escalades/packages

here is another
EXTm
500+hp/500+lbft of torque
http://www.motorcities.com/contents/02JSA404561535.html

Even with the massize horsepower numbers the Escalades aren't really quick. I guess the extra power goes to carrying around all of those electronic goodies :)

I don't know about Escalades but my wifes Denali is damn qiuck off the line. I've been thinking of taking it to the track just to satisfy my curiosity.
That 6.0 launches real well though. I managed to smoke a Honda S2000 up to about 60-70mph from a dead start. He was alone and I had two others in the truck with me. We all got a good laugh out of it though. Matter of fact, there was a kid in a convertible 3-series BMW that tried to keep up with us but we both smoked him.