DOnt worry about weight.
Train for the pump and the feel of the muscle. I know a top amateur where I train, dude sometime does drop sets down to the BAR! just pumps them out, his arms are HUGE! Its more about ISOLATION than movin BIG WEIGHT.
Some guys are HUGE and they dont lift upser heavy weight..just make sure your getting a good pump- and stimulating the biceps..
Hell, If I start with barbell curls, I only work ou to one 45lb plate on each side, for 4-6 reps..then Ill drop that down to the 25 on each side and brin them out.
Then I move to Seated dumbell curls, 45lbs, 55lbs, and maybe 60lb... usually ill stay with 55lbs
Then i go to preachers. I just keep the 25s on both side, and do lots of reps, 3 quick sets.
Then its to double bucep concentration curls, jus tlots of reps..
hope this helps..