The size aspect is one of the few downsides I can think of when it comes to this amp. Thought it's not the only amp in the world to feature a large external power supply, the HA-300 is also rather tall and extremely heavy. So you really must have the space for it on your rack or desktop.
I ran into trouble when I tried running my ModWright Instruments Oppo 205 (with external PSU) along with the HA-300 in a traditional audio rack (multi-tier, 20" wide). The umbilical cable on the Cayin could stand to be a bit longer.... or maybe give us an option of buying a longer one. Switched to my wide cabinet stand and the combo sounded amazing together, worth the effort for sure, but it's something to consider when planning out your system.
The documentation says side-by-side the power supply and the amp are 17.4 inches wide… Is this correct?