I don't know much about the Thermalright Ultra, but I will tell you that most people on here will tell you to buy a Noctua NH-D14 or some other Noctua cooler.
Looks like a clone of the original Noctua with the 120mm fan. You might get away with it if your 'case' is that stand thing I just saw on google images.
Don't take this as gospel as I am not sure of the testing circumstances.. Buuuut.. I recently read a review of the NH where the dood removed first the end fan (1c rise) and then the middle fan (another 1c rise) for a total temp increase of 2c.
However, either I didn't read it in depth or he didn't list how he was running that setup.
Mind you let's face it, Noctuas hardly shift the most air they're just quiet. Other fans can shift up to double the CFM with double the noise. So yes, I would say you could do that BUT good luck. The Noctua comes with the clips mounted onto the fans with rubber grommet things and I wouldn't try to remove them on account of -
You would need to seriously bend the clips then bend them back risking snaps.
You could easily rip the grommet destroying it. And there would be no way back nor recourse as your warranty would be void.