M-Audio M-Track Plus and Cubase - Low Volume

I’ve recently been using a new audio interface M-Audio M-Track Plus, Cubase LE software came with it. I’ve managed to get some decent tracks laid down after a bit of a learning curve and a few derpy forum posts, more to come I’m sure. Is this one?.
Now that Cubase is feeling more user friendly and the creative juicy sunshine times are flowing, I’m attempting to improve my experience.
There’s got to be a way to boost the output? Listening with headphones through my M-Track, it’s really quiet. I don’t want to go def but if I could push out another 15-20% it would make all the difference (especially when recording drum tracks). It’s not a cheap headphone thing, when I plug 'em into my iphone I get at least twice as much volume.
Any suggestions?
Any other M-Track users experiencing this?
Is the M-Track under powered?
Cubase is great.

After figuring out if I turn up the direct/usb knob I get some more volume. However, when I do this, the sound will completely cut out and Cubase prompts “hardware not found” and shows me a selection of drivers to use instead.
This also happens occasionally when I am recording, for some reason the program or my AI must think the signal is too strong or something and up comes that prompt. Very frustrating.
I’ve used an earlier version of Cubase years ago and if I had a input signal that was too loud it would sound like crap, but it would keep working…

Now I realize the Direct/usb know is for mixing the playback and input levels. So this doesn’t help my original issue.
Sigh. I think I’ve wasted money on the M-Audio.