try 1750 first, 1750 is safer , 1500 is more tight timings you are copying to higher frequency.. If 1750 brings some good improvement then you dont need 1500.

And last time I forget to mention  : install amd 17.12.2  drivers , and from radeon--->gaming--global settings--change gpu workload to: compute  ...and  be  sure it stays  like  that, even after restart.. This is very important..