Calculating DOF voigtländer 17.5

Hey guys!
I am looking to get a 35 mm equiv. fixed lens combo, and I am considering the following:

Fuji XE1 / upcoming 23 f1.4 
Olympus om-d em5 / Voigtlander 17.5 f0.95
Sony rx1 (35 f2)
In my considerations I was wondering, with which of the three is it easiest to achieve the narrowest DOF? And how do I calculate this for the future, any good links?

Thanks in advance!
Klaus