redline man, rpm is your friend. increasing RPM increases your HP.
also, every gear has a certain amount of torque multiplication. 220 ft/lbs of torque is not enough power to get a wrx moving from a standstill, at least not easily. therefore they put "lower" or "shorter" gears in the car which multiply the torque output a great deal. the drawback, you can only go so fast before you have to shift to a higher gear. so, 1st gear puts a ton more torque to the wheels than 2nd gear, and so on, so the longer you spend in the lower gears, the harder you accelerate.
there is a long, drawn out way to figure out the precise rpm you should shift at, but its a lot of work just to find out that 99% of cars should just run to redline
but you've still got that whole torque multiplication thing. i don't know if you realize it but you're actually putting like 500-1000 ft/lbs more torque to the wheels in 1st than 2nd, and it gets less with every higher gear.
man just go to the dragstrip and make some runs shifting at differnt points and see the for yourself instead of taking my word or anyone else's.