I'm not a big fan of pyramiding....but different rep structures work better for different people. I found that I gained best by doing 4-6 reps and using heavier weight. I would use enough weight so that I could do at least 4 reps, but no more than 6. If you want to bulk up, heavy weight and low reps is the way to go. I would do 9 total sets per muscle group, with varying exercises.