220 watt power supply? Wow, that's weak even for Acer.
Power supplies can usually be swapped out. Most OEM machines use ATX formfactor power supplies (ATX12v 2.x electrical specifications) but some machines may use the tinier SFX formfactor power supply. The SFX formfactor is electrically compatible with ATX12v 2.x but has a different shape.
You need to find out the physical dimensions of the current psu.
I suspect that it is smaller than a standard ATX psu.
A ATX psu will be 150mm wide, by 85mm high, and a variable length. Probably from 140-180mm long.