Hello, I'm debating whether to buy the reference gtx 980 SC or the gtx 980 SC with ACX 2.0. Would the reference one be better build quality than the one with dual fans?
Thanks.

 
Basically the ACX2.0 has more effective cooling than the 'traditional' fan, particularly on an open bench, but since much of the air exhausts into the case instead of out the rear, airflow in your case becomes a significant factor in your decision, and possibly having 2 cards instead of just 1 would also be a factor for the same reason. From what I've read, the ACX is quieter on load (or is supposed to be). Hope that helps. There's several threads on this already I believe so try the search thingy.