Hi,
Your K50 is also server, I wouldn't drop this kind of feature so quickly.
have owned Cary DMS 500, and DMS 600 in the past, they are nice but far from "big boys" league. Owning MSB Premier DAC and Luxman D10x, feed buy Melco server, the first one (the MSB) is the better sounding.
I have heard the Grimm M2 several times, while its great, to my taste I still prefer the MSB, even When fed from render and not the ProISL module.
Someone here mentioned the Watson audio: Madison LE, its quiet surprising little unit (the company used to design the DAC board that CH used in its receivers\dacs before CH bought it)
Out side the MSB Premier you might check Esoteric N-01XD, a second hand Linn Klimax DSM or the Naim ND 555.