http://en.wikipedia.org/wiki/American_lion
Gee, I kinda questioned wiki. Male African lions in the wild have been weighed at 500-600 pounds. But depends on where they are located. And According to my WildBook (magazines that I used to get as a child because i wanted be Zoologist), the American Lion's skull was about 50 % percent bigger, giving credit to an estimated size of 800-900 pounds.It skeleton was about 50 % bigger as well. Being able to bring down American Bison. Maybe new evidence has changed that.
Now the Sabre tooth cat (Smilodon- there were several, but this one is the infamous one) had thicker and large front leg bones, which many thought it was more a stalker than a runner, and it its huge front body was used to subdue prey, while it stabbed it.
What I want to know is when will they clone a Smilodon, because I think that they have found hair samples or frozen ones in the Tundra. Since in theory they are close cousins of the Lion, all they really need is sperm or eggs, and create a hybrid. They were think about doing that with the Wooly Mammoth's that they found in the tundra. Probalby look like some type of Mastadon.