HD 5670 1Gb DDR 3 is Ok?

Umm. DDR3 is used in RAM, GDDR5 is used in video cards. GDDR5 is faster. 5670 is old and it wont support future games that are at least some GPU intensive (you'll surely lag). Go for nVidia GTX 460 in SLI (get 2 cards if your mobo supports (has 2 PCI-E x16 slots) even single is better than 5670), 68xx, 58xx, or any GTX-series.