Crossfire 7970's is better really. JackNaylorPE is right that a fix for the micro stutters is coming soon. You could always buy one 7970 though and buy the second in a month when the fix comes out.
Either of the AMD options, the 7990 or crossfire 7970's will easily beat the Titan by a long shot.
The only other option you may want to consider is waiting, as the new AMD 8000 series are probably going to be out at the end of this year.