I'm currently using a Blue Circle USB Thingee and have owned a M2tech HiFace and to my ears, in my system, I find the Blue Circle superior. It had a more organic presentation. I found the Hiface slightly tipped up in the high frequencies which eventually I found tiring. The Blue Circle is also more accurate in terms of instrument timbre.
One drawback to the Blue Circle Thingee is that its limited to 16/44.1 - Blue Circle does make a pricier model called the USB Tunnel, which handles up to 24/96 I believe.
Another issue for me with the HIFace was that when I matched movies on my Mac Mini there was an lag in the audio which I could never solve. M2Tech acknowledged this and basically said the only fix was to use dvd software which could adjust for this. Not sure if this is relevant to you but I thought I would throw it out there.
Good luck in your search. I recently dove into the whole computer/audio world with a Mac Mini/Pure Music and USB thingee and couldn't be happier.
One drawback to the Blue Circle Thingee is that its limited to 16/44.1 - Blue Circle does make a pricier model called the USB Tunnel, which handles up to 24/96 I believe.
Another issue for me with the HIFace was that when I matched movies on my Mac Mini there was an lag in the audio which I could never solve. M2Tech acknowledged this and basically said the only fix was to use dvd software which could adjust for this. Not sure if this is relevant to you but I thought I would throw it out there.
Good luck in your search. I recently dove into the whole computer/audio world with a Mac Mini/Pure Music and USB thingee and couldn't be happier.