Connect 2 external monitors with MacBook Pro
I have a MacBook Pro Retina. I connected a 27" Asus Display directly to the HDMI port, and a 27" Samsung Display to the Thunderbolt port through a DVI to VGA adapter.

I now have three displays stacked horizontally, with quite some nice real estate. Both external displays are 1920 x 1080 and have the Mac with Retina resolution of 2560 x 1600. You can do at least the same with your 15" MacBook Pro Retina.

Hope this helps!!