I looked at them... chose to go with the Hypex NC400s as they measure pretty closely and have a higher gain. The Purifis looked to really require an input buffer/op amp and I just don't have the knowledge base to comfortably understand that. The Hypex Modules are pretty straight ahead.
I looked at Ghent but couldn't find confirmation about whether the Chinese Aluminum Chassis would incur any tariffs. One source I looked at mentioned a possibility to be as high as 80%! I haven't pursued any further due to other things getting in my way. Soon, though!
For the Amplifier modules, if you order those as components, they should be duty-free. At least, mine were from Hypex.