what is your
max budget for gfx card?
gaming resolution (display res.)?
psu model (+12v rail's amps)?
i'd say oc your cpu with a good cooler and get a gtx 560ti.
2x 5770s would indeed deliver increased fps except the problem of microstuttering. single 5770 is quite capable for gaming. it's so good that amd decided to not update the card and simply rebadged it as 6770 to fit into the newer 6000 series.
if you're okay with microstuttering and won't upgrade your whole rig for a year or two, get a second 5770. otherwise, stick with the 5770 till ivy bridge/piledriver comes out and decide then.
tom's gfx card hierarchy chart (very useful): http://www.tomshardware.com/reviews/gaming-graphics-car...
Sell your 5770 and grab the 6950(may unlock to a 6970)... if you wait a bit til the 7xxx series get out more, the 6xxx series may drop lower in price... just a thought.
... I have the 5770 also, and it does run rather well on these new games. I would wait a month or two and see if prices drop... no NEED to upgrade now, your card can handle any game now... just not ULTRA settings.