2x4 Pin question

[WeedyBiscuit]

Hi,
I am upgrading my power supply. I have an intel DZ77BH-55k. The motherboard says to use s 2x4 power adapter. I have been using a i7 3770k. I plan on doing minor overclocking. Do I really need a 2x4 adapter? Can i just use a 2x2 adapter and put in in the right side? If I need one, can you recommend a cheap power supply (under $85) that has a 2x4 power cord and can handle crossfire/sli? Will this supply work http://www.newegg.com/Product/Product.aspx?Item=N82E16817517003?

Thanks

 

[AMD Radeon]

http://pcpartpicker.com/part/xfx-power-supply-p1750snlb9
and
http://pcpartpicker.com/part/corsair-power-supply-cmpsu750txv2

nothing below 80
and the corsair one is better, even it comes with 4x 6+2 pcie