Thought...they don't make many 300 watts PSUs these days, so is this an older one with or without 24 pin atx?
Gigabyte GA-G33M-DS2R
Power Connectors 4-pin ATX12V connector, 24-pin main power connector.
This is also going to depend on the quality of the PSU and what graphics card etc it's going with.
Onboard graphics I guess?