My first pc build for gaming. What do you think?

[sDGam]

I recently decided to build my own computer mainly for gaming and after some research about the hardware i picked this build :

[CPU] Intel Core i5 3570 (s 1155 , 3.4 GHz , 6MB) (215$ @newegg)
[GPU] Sapphire HD 7970 3GB GDDR5 (300$ @newegg)
[RAM] Corsair RAM DDR3 4GB Dimm 1333MHz XMS3 x2 (45,70$)
[MotherBoard] MSI Z77A-G45 (s 1155, Z77, DDR3) (95$ @amazon)
[HDD] Seagate ST500DM002 500GB HDD 3.5" (16MB Cache, 7200RPM, Sata 6Gb/s) (59$ @amazon)
[SDD] Samsung 840 Series 120GB SSD (2.5, Sata 6Gb s) (97$ @amazon)
[PSU] Corsair VS Series 650W (CP-9020051-EU) (88$ @amazon)
[WaterCooling] CORSAIR Hydro Series H100i Water Cooler (110$ @newegg)

Total cost : 1,055$

First of all, as a newbie, i am not sure whether all pieces are compatible with each other or not.
Then, i need some opinions regarding the GPU. The one i picked costs 300$ and i think it might be too much for my needs. I was thinking of equiping Sapphire 7870 2GB OC which costs 185$. I am not an extreme gamer so i am just interested in being able to play even the latest games on decent graphic settings (my current pc is so old that i play WoW on average 20 fps)
Another concern is the cooling... Is the current watercooler i picked too much for this build or should i pick i cheaper one or even change to air cooling? (I might use overclocking in the future. I am cleaning the dust off my current fans twice a year)
Last thing i need to know is the way HDD+SDD works. I use the hdd for storage and sdd for speed or?

You are welcome to suggest replacements for any piece

 

[Havoc2510]

1) Water cooling is just not necessary at all for a CPU that will never be overclocked, it's just a huge waste of money! For that CPU you could get a Freezer 7 Pro rev 2 or a CM Hyper 212 Evo and save a fortune!!!

2) You may want to invest in 8GB 1600MHz RAM, as I personally think this is best for gaming and reg PC usage.

3) I would get an Nvidia GPU, maybe a 670 or 760 depending on what you can get for the same price in America.

4) Games take up a huge amount of space, and because hard drives are relatively inexpensive, I would get a 2TB Seagate Barracuda 7200.14 and never have to invest in storage space again!

Hope this helps