Decent AMP -- Power Supply broke and no drop support.
Amp is good, sound quality is good, but the power supply broke after about 2 years of use. Drop said only way to get another power supply from them would be to buy the amp again. Luckily you can do some digging and get a third party power supply.
Luckily, I also own an SMSL SP200. The SMSL is essentially the same technology; however I'd say it is the better buy. It measures better (if you care about that), the build quality is excellent, the sound is as good if not better. In addition, the actual interface is much better. An annoyance with the DROP 789 is that the input and power buttons are push buttons, which made it difficult to troubleshoot problems with the amp and you also cannot see at a glance what input the amp is using. The SP200 on the other hand has switch that toggle to clearly identify settings so at a glance you see what input you're using. Will update the review if I have any problems with the SP200 but bottom line, it is 100% the better choice over the DROP 789.