For bicep dumbbell curls, what's your max?
Red, have you tried Jack3d or 1MR yet?
Also, yes, strong legs = strong everything else. Protip: strong core = even stronger everything. I had a buddy that only worked out specific muscles and hardly did legs that was toned and as soon as he worked out his core that fool got mad ripped.
If you're talking to me, I usually max out around 40. Any more than that and I start swinging and using my back after a few reps which I won't let myself do. Perfect form always. But if I can get like 4 in with 45, ill do a dropset and hit the 40's, and then maybe the 35's for a few extra reps to get max overload.