sorry I don't know these things :(

 

I always work back from the quickest render time to an acceptable image - rather than the other way around so I don't muck around with the sexy stuff!

 

I'm always relying on post work, ( i render a coverage and shadow layer as well)

 

I  reckon that image (last) taken into ps and sharpened would be pretty good, also adjusting the levels would help in post, plus I use oloneo hdr on single images and  that tweaks them as well

 

but it's not the answer you are looking for sorry