With quality media best would be to use the rated speed in some cases you can overspeed it and get still fine results. For media i'd recommend Taiyo Yuden or Verbatim.
Both media would give you an excellent result. Personally i'd go with TY 8x media burning at 8x and Verbatim 16x media burning at 12x, which could your rebadged BenQ 1640 handles very well.
And for the RW it makes many people confused it's just the logo, look only on the package for example DVD+R, -R, +RW etc.