Hi,
I suggest you make a custom fan curve within Evga Precision X.
If this doesn't help, then reapplying thermal paste might be a good idea: MX4 is a good one.

What is your temp when idle?

How many fans in the case and where?  
 
I run a i5 3570,  i don't overclock anything.  Most other people will probably need better cooling for their pc.
I am also a new owner of a 770 ACX 2gb.  Purchased in August and was very lucky with setting it up.  From reading a lot of posts around different forums,  i felt that the idea of moving the air away from your card/mobo and out the case was most important for ACX coolers.
 
Buying the card was a lot as i wasn't planning to upgrade till Christmas.   I knew i needed better cooling and didnt want to spend much more.  I took a chance on buying just a bigger fan (200mm fan to move air out from the top)  My case(older CM HAF) has 2x120mm fans,  one intake and one exhaust.
 
Like i said i got lucky with buying that one fan. 
-Idle temp before was 33-34c and under heavy load pushed it to 62-63c.
-Idle temp after(with 200mm) 24-27c and heavy load never went above 55c.
-fan speed for me is 40%-60%.
 
Funny and stupid story,  200mm fan does not fit in my case.  I saw a review that said modifying it can make it work with my case and the fan was really liked by a lot of people.  So i had to break off some of the mounts for the screw holes to make it more round.  It is all plastic so i was again lucky to not break the whole fan.