Help me decide which GPU to buy!

[Mastrec]

Hello everyone, I have browsed this forum for a week now and have finnaly managed to design my ultimate pc for music production and gaming. The only problem is that I can't decide which GPU to buy, there are so many different version and which every version there are different companies that make them.
Here's my plan:

Intel i5 3570k + TX 3 EVO
ASRock Z77 Pro3
Corsair Vengeance 1600mhz 2x4gb cl9
Seagate Barracuda ST1000DM003
Corsair CW 500W
Cooler Master K380
A GPU around the lines of a sapphire 7870 or msi gtx 660 tf

Please critic my build as it is my first one and thanks in advance for helping!

 

[Mastrec]

Oh and I was wondering if the Corsair or the XFX Pro 550W is better?

 

[tiny voices]

The XFX is a better PSU. It is made by Seasonic.

Get the 7870 XT/LE/MYST version. They are much more powerful than the normal 7870 or the 660ti.

 

[greddygutz]

how much do you want to spend?