Time to dive back into some rendering tech.
Image Based Lighting, a great technique for cheating. We all know GPUs are incredibly powerful right? Well they still just aren't powerful enough so we'll have to do some more approximation cheats again.
Take a nice skybox, blur the crap out of it (technical term) and project it back into your scene and based on your nice BRDF material system you can apply some of the sweet skybox colour and get some pretty decent looking lighting quite cheap.
Then when you realise you aren't using smooth normals on your models, it'll look a little better :P
Finally add a smattering of SSAO and voila, not bad.