First Computer Build for Gaming HELP NEEDED! ~1000

This will be my first build and I will be using my pc for gaming, schoolwork and to watch movies.
The games that I will be planning to play are skyrim, minecraft, assassin's creed etc
I don't think I will be playing that many games,however.

My budget is currently at 1000 USD but I don't mind spending up to 1,250. Also, peripherals will not be included in the budget.
I would like to buy my parts from newegg/amazon


Here are the parts I know I'm going to get
CPU : i5 2500k--------------$220 @ newegg
GPU : GTX 480--------------$200 @ newegg
Case : Antec 902 v3-------$ BOUGHT FROM BESTBUY FOR $70
Cooler: H100----------------$BOUGHT FROM FRIEND FOR $65 (will have rad set as intake on front 120's)

so far the cost of this is roughly $575. For my budget, there is $425 left but I'm flexible to add on


Here are the parts that I shall get but not sure about choosing
Motherboard: Undecided about the chipset Z68 or z77 help me here
PSU: unsure about wattage please help me here
HDD: 750gb or more
SSD: I am not sure if I really need one because they are expensive

What i need help with is for you guys to help me choose the last remaining parts for my build

THANKS IN ADVANCE!