You appear to have a really nice start there... Can you show a clay render using the derault Scanline render? What 3D App are you using and what render engines to you have access to, as that will make a difference in how you setup an HDRI Scene.
Some Good Tutorials that I've used:
Max/Brazil:
http://www.tutorialoutpost.com/count/1886
Max/Vray:
http://www.aversis.be/extra_tutorials/00.htm