Ah, a discussion! Bring it on!
I'm the proud owner of 4 ADA8000s. I have and do use them professionally but...and a big but...I still think the pre amps are rubbish. Turn the gain up beyond about 3 o'clock and the noise makes them unusable. However, I can get away with them for live work, especially as (when I was doing lots of theatre stuff) all my radio mics had line outputs anyway--and the rest I could use with "non money channel" mics that I knew would be happy with very low gain settings.
If the ADA8000 uses the same pre amp circuitry as Behringer mixers then I call rubbish on them too--and my experience with them bears this out. I could get away with them if I kept the gain nice and low but woe betide me if I had to crank them up.
Now, I also have a cheap M Audio Mobile Pre which I use for a lot of mobile stuff. The mic pre amps are nowhere near Rupert Neve (heck not even near Rupert the Bear) but I can still crank them up all the way with no audible noise.
The Mobile Pre is my only stand alone interface now (my "big" interface is a digital mixer) but my experience with previous AIs is similar to the Mobile Pre. I'm sure there are rubbish AIs out there as well but, in my experience at least, $150 spent on an interface will get you better quality than the same money on a mixer, if only because of the money the manufacturer has to spend on useless toy EQ sections, useless toy effects units, cheap faders rather than cheaper pots and so on.
I should say that I definitely WAS talking about mixers with USB out since, without that, the OP would have to buy a mixer and an interface anyway.
Finally, a point of agreement. Yes, if you have a decent sound card in your computer a mixer (probably more than $150 though) makes eminent sense. However I challenge you to name a single computer that comes with a decent (much less good) sound card! Until you get into the specialist AI market (PCI or external) they just don't exist!
Apologies to the OP for diverting your topic...David and I agree that you need an audio interface, not a mixer. We're just discussing why!