This scene - and old one I did for testing bagginsbill's environment sphere - consists of the car, Miki2 and bb's env sphere with an HDR image mapped onto it. That's all. This was rendered with 1 infinite light, 1 IBL and IDL turned on (modest settings). Despite the complex shaders on the car, it rendered in around 4 minutes.

I did a version with IBL off but didn't keep it for comparison - I don't think there was a huge difference.

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Windows 10 x64 Pro - Intel Xeon E5450 @ 3.00GHz (x2)

PoserPro 11 - Units: Metres

Adobe CC 2017