Which DACs are known to be sweet/rich/relaxed?

+1 for converting your ethernet line to optical in between the server and streamer if you haven't already. x2 converters, x2 transceivers, and an optical cable costs $100, and place a low noise power supply of your choice on the optical converter nearest the streamer. That should remove some graininess. Might push the sound in a direction you'd like. 

If you’re looking for a tube Dac the Nagra tube Dac might be an excellent choice it is worth trying!

Best of luck 

I personally prefer the DACs from Playback Designs with their FPGA-DACs.

There can be huge discrepancies with recording quality. The majority of the worst recordings I’ve heard are rock, particularly early early cd recordings using DDD engineering. If you tell me Dark Side of the Moon sounds like crap then there is something amiss in your system. Please be specific regarding which recordings you expect to sound good that instead sound harsh. Throwing more money into your system isn’t necessarily the panacea.

I would suggest those incisive speakers and amp will negate DAC change. It is always happening that pursuit for clarity where suddenly the musicality seems to have gone and you spend listening time finding the faults rather than enjoying the music. I'm at a place now whwith tannoys and luxman that I like. There is clearer there is more transparent but I find myself lost in music more now compared to when it was all pres and monoblocks and a spaghetti junction. 

If I started over probably a 6w valve amp feeding klipschorn