I had and enjoyed the H390, and currently have Wilson Tunetots, though not both at the same time. If I had put to a $ figure on the performance of the DAC and streamer sections of the H390 I'd say about $1k and $500, respectively. They are pretty good as part of an all-in-one solution but you can certainly do better. The nice thing about the H390/590 is the DAC loop feature, so you can upgrade just the DAC for now and feed it from the H390's streamer via BNC, then have the option to upgrade to an external streamer later. Don't skimp on the digital cable though.
It's a wide world of digital out there. On the "lower" end of upgrades for the H390 I like the MHDT Orchid DAC and SOtM sMS-200ultra streamer. I also used it with a dCS Paganini DAC and Network Bridge, which was better overall to my ears, though not as rich sounding. I think your speakers can really take advantage of what a higher end DAC has to offer, namely soundstage depth and inner detail, and the H390 will deliver those attributes.