A GeForce GTX 650 would work fine with the Shuttle PC61J 300 Watt power supply since the power supply has a combined +12V continuous current rating of at least 20 Amps and has one 6-pin PCI Express supplementary power connector.
Oh okay, I thought it's only 16 Amps because of the "+12V1: 16A / +12V2: 16A" specs written on the PSU.
I want the GTX 650 because of the low idle power consumption. I saw it here LINK: http://www.guru3d.com/articles_pages/geforce_gtx_650_msi_power_edition_review,5.html
Thank you very much for your comment. I will get the GTX 650.
You should have the best answer.