Hi, I want to add a graphics card to my Apire tc-895 but I need to upgrade the PSU as the stock one is only rated 180 watts

However looking at the back of it there is no cut out to install a larger unit that I would require (see attached picture). The existing opening is only about 2 inches square! Does anyone know a way around this in order to increase the opening size without wrecking the case, or does there exist a compatible PSU as small as the 180 watt stock version with around 650 watts? I bought this in order to upgrade it but if I cant replace the PSU I cant do anything to it! Any suggestions welcome, thanks.