@wvhemis I'm glad that you're overall liking your DDSRT. on the topic of the HK stereo, below is a post where we really dug into the EQ settings and what it does for the HK sound. the short version is once I set my EQ to Bass: -4 Midrange: +5 and Treble: +2 the HK really came to life.
lots more details in the posts. the really important setting is the Midrange: +5. some members agreed with me on the sound, some didn't agree. I encourage you to read over the posts and use those EQ settings as a start and then tune to your personal preference.
Harman Kardon correct EQ settings (Alpine also) - try these