One of the utility DSP's can be used to run external processing on your files, which, I guess, would mean that you can use SoX from within dBpoweramp. I haven't tried.

I do not convert my pre-emphasized CDs. I tag them, and I use a media player with a plugin that recognizes the tag and applies the EQ on-the-fly (namely, foobar2000).
(Also, in order to make sure I have them identified even if I should screw up tags, I use a different file format, namely WavPack in place of FLAC).