My first build, any changes?

I think it's time for me to finaly order my new computer this weekend. I'll mainly use it for gaming, but i will also use it for a bunch of other things, including video and sound editing. I live in the Netherlands, thats why you'll see so many Euro signs. 1 Euro is about 1.3 Dollars, but the strange thing is that when I search the price of every piece in dollars (on pcpartpicker) I come up with almost the same number, but than in Dollars (so 1:1). This is too the explination why I pay so much for my hardware, this is where I'm looking at:

                Sapphire HD7850 2GB GDDR5 (NOT the OC version)  

                Sharkoon REX8 Value Edition Midi-Tower 4x USB 2.0 2x USB 3.0 Window (Black)

                Asrock 970 Extreme3 AMD 970 AM3/ AM3+ 4x DDR3 5x SATA-600                         

                AMD FX-6300 3.5Ghz AM3+ Box               

                Western Digital Blue WD10EZEX 1TB 3.5" SATA-600

                XFX PRO 550W (yes, it is 80+, 85% perciceley)

                LG GH24NS95 24x48x SATA-150 (Optical drive)

                Corsair Vengeance 8GB DDR3 1600MHz (2x4GB) CL9    

It will cost me now:578,60 ($755.21)

My actual budget is 625, so there's room for an upgrade

First of all, I don't know which motherboard to chose, there are so many, that I don't know which to chose, Maybe an upgrade to the Extreme 4??

Do I need an ssd? and if so, which one, and how many gigs?

The ram is now the cheapest 1600mhz ram I could find, do I need 1866mhz or 16 gigs?  (I like to play with big files)

Any other suggestions are appreciated.

Thanks for your time.

Casper

(PS. I want to thank Tek Syndicate that all the noobs like me can ask questions and get a proffesional awnser, great job)

This build looks great! The only thing I would change is get the ASRock 970 extreme 4 because it gives usb 3.0 service to your usb 3.0 front headers. And i would recommend an SSD for your OS, it speeds it up alot. I would try to get the biggest possible because it will turn into you C drive, but 64GB will be fine as long as you move all your files into another drive. Good Luck!

will the SanDisk 64GB 2.5" SATA-600 SSD  make me happy or just make me cry, because it is € 54,45, which is cheap, maybe too cheap?