I understand that you would rather have the 28 for less, who wouldn't, but this new 28 is a significant upgrade over the previous model.
Revised dac, new amp, tweaked power supply, new volume control, shielded case. You also have to consider that the old 28 amp is from the days of the Phoenix circa 2009. Audio-GD has come a long way since then.
That said, Kingwa is good guy. Shoot him an email and see what happens. It's currently $712.50 because of the sale, he might accept $680 if you're reasonable.