According to an equivalent card at newegg, you need 24 amps on the 12V rail. 18 amps isn't close enough. You need a better PSU. The one you mention outputs up to 34 amps on the 12 volt rail, so it will be sufficient to power that GPU.
As in the Corsair Builder will be sufficient? And is the 24 amps requirement only a recommendation for 'max load'? If so, the PSU I currently own would be sufficient for low~mild load tasks, correct?
Thanks for your help, I really do appreciate it.