In my opinion CamExpert would be the place to use for this. Having an individual hand machine the chassis seems insane to me when their are automated systems to handle stuff like this. Not to mention the advantages of the software, engraving, etc.
And I don't think any of the SumR trafos I've gotten have had any mechanical hum. I've got another one on the way now so I'll check that but I also have one downstairs that I'll try and fire up tomorrow to check (it's a fully potted and shielded unit). Plitron is not without its faults as well, I seem to remember having a conversation with a manufacturer about them and learning that under full load they tend to sag and consequently you have to guess and overspec them to get the desired output. I can't help but feel like they have some good marketing people who've gotten them a good rep and now feel free to charge a premium for their goods.