I think I've figured out the "Save the cheerleader. Save the world." comment. If Syar is really stealing powers by killing the "specials" then he could gain Clare's healing factor if he kills her, Monday. Now a buddy of mine told me yesterday that he thinks the date on the newspaper Hiro read in episode 2 was November 20th, which is the show's next air date, and the episode where Sylar, Clare, and Peter meet. So if Sylar get's Clare's powers, he coudl easily appraoch the nuclear guy and survive the massive radiation, thus getting close enought to kill him and set off the explosion. However, if he can't get Clare's healing factor, then the nuclear guy may be able to kill Sylar by just being in proximety to him when Sylar tries to eat his brain.
Gabriel