My first recommendation is to check if you can test the card in a different system that has a better power supply, that is to verify the card is not defective.
Secondly, if you invest a lot on CPU+GPU it is wise to invest on a good power supply that can power those components in the long term.
Get a power supply that has 80PLUS certification, these power supplies are very efficient depending on their rating. As an example in your case since you live in Canada, a 80PLUS Gold at 20% load has 87% efficiency and the rest is waste (13%) which translates to heat. At 50% load is 90% efficient ant 10% is waste or heat. Cheap power supplies are not very efficient therefore if it is lets say 70% efficient, 30% of waste will be translated to heat. In short, you save money in power usage and less heat in your PC.
Now, Single Rail power supply design has its advantages as you can take the full rated power to power all components. Multiple rail design will be split but it can safeguard better components if the power supply fails. Most new power supplies have good power protection so you can go either way.
I hope this helps.