It's actually probably a couple amps straight 12v. I have a Samsung 15" LCD and the power supply says it is rated to output 12V at something like 2 amps, and I'd think it's unlikely your 15" takes 10x power.
I tried to run my 12V 10.4” TFT from the Opus. I found the Opus could not handle the inrush current when I switched on the screen. You can read all about it in my post called limit inrush current (which is not solved yet by the way).
I would be interested to know if you succeed with your 15” LCD on the Opus.