i7-2600K and GTX 570.
You can use the memory, but the PSU is better upgraded to an 850W model.
I concur with Harm's recommendation. The Quadro 1800 is obsolete: It is based on the equally-obsolete GeForce 9600 GT but with only a 192-bit memory bus instead of a 256-bit memory bus. As such, the only memory configuration that was available on the Quadro 1800 was 768MB. Unfortunately, Premiere Pro CS5 requires a minimum of 765MB of free, unused graphics memory just to even enable GPU accelerated mode at all even with the hack. But since Windows itself eats up some of that 768MB, you'd be left with less than 750MB of free, unused graphics RAM with that Quadro 1800. As a result, Premiere Pro CS5 will be stuck in software-only mode even with the hack if you have the Quadro 1800 as the primary card.
so can i setup dual PCIx16 GTX285 (supported) & quadro 1800 ? its stronger more than GTX 570 ?
Premiere does NOT use dual cards (and it may cause problems) so if you have a GTX285 only use one
Since the 570 is newer, I would use that instead of a GTX285
But, as I said, if you already HAVE a 285, use that