Can my 300w handle this card?

Unfortunately that won't be enough. According to AMD "400 Watt or greater power supply recommended" (http://www.amd.com/en-us/products/graphics/desktop/5000/5670#).
Let me know if you'd like some recommendations on affordable good quality PSUs that will do the job
 


I'd recommend staying away from corsair especially if you have access to an xfx. The xfx PSU you've mentioned would be great for that GPU