Just remember...at these ranges ( 1.2, 1.4, 1.8...) there is a razor thin DOF which may or may not be your desired effect. If you want a 6 inch DOF...great!. If you want 2 people to be in focus.....You will need to close it down and add some light! People forget this ofter and just shoot wide open....and wonder why the nose is sharp, and the ears aren't!
Actually with a crop body and a 30mm lens, f1.4 provides pretty good DOF if you aren't right up close. For example, f1.4 at 10 feet has about 2 feet of DOF. THat's enough to get everyone on the same couch in focus for example. If not F2 has about 3 feet and f2.8 about 4. That is why I like the wider primes for low light. You need shorter shutter speeds to handhold and they have workable DOF even at f1.4-2.8.