TDP = max power draw of the PC. That's what you want to consider for power calculations.
It might work, but only if you keep from powering anything else off the 12v rail of the M3.
That means no full-sized HDD.
That means no powering the LCD from the M3.
That means an optical drive must be chosen carefully. A full-sized unit is right out.
The power calculations would be too close for my comfort.