I want a minimum of 100 lumens, and would feel more comfortable having access to the 150-200 range. A large section of my nightly commute is dark rural style roads. I usually run my Fenix on the 3rd brightest setting there, and the 2nd highest (100 lumens) in neighborhoods. When I'm going fast 100 lumens borders on too little.

EDIT: Might go check out the axiom lights at my Performance Bike. I remember they had some decent looking ones in the 30-50$ range, and the tail light I bought from that brand works nicely.