That power supply will probably limit your overclocking. Other than that, it's good enough.
And no, that power supply won't be good for SLI. Not by a long shot.
That system is pretty darned good, except for the two bottom lines. You need a higher-wattage quality power supply from a good company, and right now that graphics card is your biggest bottleneck. Even with another in SLI it would still be the bottleneck.
I would strongly suggest returning the power supply and graphics card for refund and getting better ones, even if it means waiting a couple of extra weeks for the next paycheck or to beg/borrow/steal** some more money for the budget.
** No, I do not condone theft.
Edit: And you should be RMAing the mainboard soon too, unless you got a new fixed ASRock that I haven't seen any of yet. I'm still waiting impatiently to see a new version of mine.