I would avoid SLI unless you plan to play on multiple monitors. It isn't really necessary at 1080P and you run into unnecessary heat and compatibility issues.
I would aim for something along the lines of:
8GB DDR3 1333Mhz
~500GB 7200RPM hard drive
HD 7850 2GB (Similar performance to GTX 570 with much lower power consumption and lower price)
500-550W PSU (Preferably Seasonic/XFX/Corsair/Antec/OCZ etc.)
Case is personal preference but the Antec 100, HAF 912, CM Storm Scout are good choices.)
You should hopefully be able to get that within budget.