Watercooling isn't 'necessary' for most builds, but more of a hobbyist cooling solution. You can do some really cool stuff (pun intended) with a watercooling loop, but it depends on your budget. I'm not sure how well your case is built to accommodate an actual water loop, so that is something to consider as well. As for case fans, it really depends on the fans being used - not all case fans are created equal.
Come visit us over in the watercooling forum if you want to get some additional ideas. I have watercooling sticky info linked in my signature below.