Which one to buy: UpTone USB REGEN or Intona USB Isolator?

[PeterG]

I vote Intona! Just added Intona between Mac Mini with Amarra and Yggy. Using the industrial version with Audioquest Carbon cable. Results are great! Installation was basically plug and play, just had to restart the Mac and point to the Yggy in System Preferences/Sound. Noise floor lowered substantially, and I have to admit that I didn't realize the floor was there until now. I just plugged in yesterday, so I'm looking forward to several hours of listening today.

This is in sharp contrast to my experience with USB Regen a year ago. As I posted then, I did not find it helpful in front of a Meridian Director DAC (compared to AQVOX).

[PeterG]

I have 4 usb ports on my imac. can i plug 4 power hungry devices into them simultaneously. eg 2 intonas, hard drive, usb dac, all at once with no impact on imac or on performance of devices?

"No impact" is a subjective term--compared to what? You'd get dramatically better sound quality by putting the same amount of money into a single DAC instead of three. But leaving that aside, and assuming you seek to run only one DAC at a time, this should be no problem and you probably will not be sacrificing much if anything in terms of sound quality compared to having the two idle DACs unplugged. You simply point to the DAC you'd like to use for Output under Sound in System Preferences. (Just to be clear, I do not think you'd be able to power multiple DACs simultaneously.) Good luck!