Oh sure, if you're an extortionist, people will hate you, but as long as your military rating is higher than theirs they probably won't declare war on you.  You can theoretically extort anything you'd like, however the better the thing you're after, the bigger military you'll need to make 'em subversive.  How much money you can extort depends on the size of your military compared to theirs, and on your diplomacy level as well.

Another way to use Super Dominator is to declare war early, pretty much as soon as you have a small military of your own.  It gives you a number of ships each time you declare war, and early in the game these ships are usually more powerful than those of the other players.