I'm a big fan of Aurender for their streamers. I believe the DAC in the A15 is comparable to that in the C2700. Before I went the A15 route new, I would purchase a used Lumin X1, which would be slightly higher than the A15 retail price. The A15 is not in the class of the Lumin X1.
The Aurendern N200 is a great streamer, but you would be spending $6K on a streamer going into the DAC2 module, which probably plays into the $2.5K class of DACs. Maybe try the Lumin U2 mini into the C2700 to get a flavor. If it doesn't float your boat, go the streamer/DAC route and unload the Lumin, you should get a reasonable price for the U2 unit.