Int'l to Int'l direct transit is fairly straight forward, you deplane, walk to the counter and walk to your next gate, it'd help if your PEK-HKG flight is actually operated by CA (check if your CX flight number begins with CX61**, then it is almost guaranteed that a CA agent would be present at the counter, otherwise you might have to wait/call for it, but 1.5hr is plenty enough, unless you need duty free/lounge time, none of which u can't get at HKG. So no, I won't change it if I were you, in fact too much time at PEK would leave u quite bored.