You could use the AD9958, although it might be overkill for your application. Then again, it might be a perfect fit for your application, since you did not specify what that is.
It's got 2 separate DDS cores running on the same clock source. You would have to put both channels at the same frequency and program the phase shift register of one of the channels to 90 degrees difference. The DDS has only 2 DACs...
Added after 3 minutes:
After rereading your reply I noticed you said "AD9858", whereas I was talking about the AD9958. I assume your "AD9858" was a typo?