That the power drops off is only half the story. The question is if you move up a gear does the increased torque overcome the additional effort needed to overcome the increased gearing. If you do the calculations on a dyno graph, the shift points are redline for first and second. Its only once you want to change up to 4th that you might do better changing up before redline.

 

+1 It seems many people forget this.

 

if your car is stock then you can probably shift in the 5.5-6k range, i have the accesport tune and see torque drop off right around 5k, my car makes a bit more torque than hp and i like to use more of the torque band when i run, it's a torquey lil bastard