Maybe I missed it but I don't think you mentioned what GPU you have, cause you said your CPU renders faster. Up until September of last year I was running a Xeon E3 1246 V3 which is 3.5Ghz four core instead of your 3.2Ghz, so I was in a very similar situation CPU-wise. While a great and trusty CPU that never caused a crash for the five years I was running it, rendering was abysmally slow for me. The more complex renders could take all night, so I finally bought a 970 and my render times for my bigger scenes went from 10 hours to 3 at the most. Eventually I replaced my 970 with a 1070 for rendering and depending on the scene could drastically reduce render times again.