Under ML 10.9.1 it is on the same screen. It has always been there as far as I can remember.
Where is the iMac sleep mode time? I don't see it under energy saver...
This changed in Mavericks. The way you have yours now with that "Prevent computer from sleeping..." unchecked the computer will go to sleep the same time the display does. If you check the box the Mac will stay awake when the display blanks.
There is no longer a separate time control for computer and display.
I don't think that's correct. As seen above. Both my first post and the guy below me posted screen shots using the SAME OS X. It's about the Haswell Chip, which I also stated above.