Drill power is not critical - you just use a sharp drillbit suited for cutting steel and drill long enough periodically cooling the drillbit with water so that it doesn't burn.
I personally made about two hundred holes in shaped tube with 2-millimeters thick walls when assembling a fence. I used a rather weak looking professional Bosch GSR2 10,7 volts Li-Ion powered drill/driver - that's a good tool, but not a tool one would consider extremely powerful, I had to recharge after about each 30 holes and drilling was certainly slower than with a 500 watts mains-operated drill, yet it was quite doable.