Just got a 20x20  today and trying to quickly get setup...Do any of you guys know how to monitor the direct input signal such as a mic in the headphone mix before it hits the computer? Every interface i've had before had a  simple balance knob that let you hear a balance between sound off the computer and direct sound.
Thanks for any help...documentation is really crappy with this unit :)

The owner's and reference manual are on-line.  I think you have to navigate the mixer and use an aux to send the signal direct, but don't hold me to that.
 
@

Set it up in the mixer tab of the preset editor ...

I have a US-16x08. The software i/f is very similar. The following is supposed to work. I believe what happens is that, with the change, direct audio is feed to the phones and main outs. There's an issue, I believe, where the DAW audio is summed with the direct audio. I'm going to guess, that for this to work, you'll need to mute your mains in SONAR (edit: or, perhaps just the track(s) (instruments/vocals) you're recording; then the summing might be very useful (if a bit latent)).
 
Default:

 
To monitor direct:

 
HTH.
 
P.S. Here's the link the US-20x20 download page: http://tascam.com/product/us-20x20/downloads/

Thanks for the help guys! I managed to record some vocals and got a pretty good headphone mix last night...at least it functional now...just take some getting used to. The terminology is different from other companies.
Thanks again!