That's the standard size front, for aftermarket, so that's good. Factory bars were much wimpier.
You don't "need" a rear bar. In fact, if you don't drive hard, it will seem like it increases understeer and harshes the ride. The benefits aren't really apparent unless you push it hard. So try it without, first.
If you do get a rear bar, remember it should be smaller than the front --3/4 is appropriate with the 1-1/8.
IMHO, YMMV...