Haven't hearxd XDP-300, but I love my meze 99 Classics paired with X7mkii. It really makes them sing!
You might love DX200 with AMP2 or AMP5, if you're using single ended connection, or AMP3 if you're using Balanced connection!
I wanted to love dx200, but it feels so beta to me. So many bugs here and there. Skipping sound, noise clicking when starting some songs, random pause and the UI is so bland compared to x7ii. But good sound though, need to choose between them in one week.