Hmmm, I don`t really use anything as a reference per se.
I guess when I am looking to improve my mixes I never use techno as a reference.
Generally I look at big time studio productions for production insights.
NIN stuff is great, because it contains masses of big sounds all crammed into a track, just like techno.
Also the new massive attack album I sometimes listen to, when working out how to get space and depth into a mix.