I've had good experiences with the NFB-12 (now replaced by the NFB-15.32) and Audinist HUX-MX1. The extra $70 for the Audio GD will get you a slightly more spacious sound, more power swing, and adjustable dac filter settings. Both have preamp outs for feeding powered speakers and other amps.
You can also look into the Schiit Magni/Modi as well as the O2 Amp/ODAC pairs.
O2/ODAC works marvelously with a newer K 701. I've read that the Magni/Modi sound nearly identical.