Well, for me it took like 9 seconds to see anything in native scene setup, but I own C4D Prime only and lack the plugins you used in scene, and you haven't mentioned your comp setup too. You can see 100 pases I run for the scene without problems, and 10 passes in HD format. Besides you could lower bump in materials, in that stage of corona its 0.02 more than 0.2. And the fabric, why is it luminous?
Cheers