Low fps?

[honam1021]

Well, fist things first, you should scale things back to get FPS and GRADUALLY increase it till you find your breaking point

also:

1080p is a set of HDTV high-definition video modes characterized by 1080 horizontal lines of vertical resolution[1] and progressive scan, as opposed to interlaced, as is the case with the 1080i display standard. The term usually assumes a widescreen aspect ratio of 16:9, implying a resolution of 1920×1080 (2.1 megapixel) often marketed as Full HD.

6x512 != 1920

I tuned a settings a bit(4x msaa), and it's near full speed now (around 57 fps at the same area):
   
Does the GPU's compute performance affect the speed of pcsx2?I read that Kepler cards (Such as the 680) have poor OpenCL performance compared to Fermi and AMD cards

[Saiki]

if you increase the load on the GPU, yes