Yes tracking with peaks at -16 and -18 is really low, but that's the way it should be. We are so used to hearing things louder, that it's hard to break out of that mindset and think in terms of what's best for the track and mixing. Remember, the loudness will come with mastering, so who cares if it's really low or quiet. Just turn up your speakers while mixing. There aren't any drawbacks to tracking that low. In fact, the benefits are you have more headroom to work with when working with plugins and in mastering. The more headroom you leave the less chance you have of squashing your final mix and making it sound like shit. If you record something with a low volume, you can always turn it up. If you track too hot, no matter how much you turn it down, you will still hear clipping because that's what it recorded and you can't undo that. I heard somewhere that -6 was acceptable when I first started recording, and now I wish I hadn't listened to them because a lot of my tracks are recorded still a bit too hot to work with and sound good, so I have to go back and re-record a lot of stuff. Just keep messing around with it and see what results in a good sounding DI.
Just FYI or a little tip... EMG's tend to make your DI's track rather hot and loud... I ended up getting a Radial ProDI box, and I ALWAYS have the -16db padding turned on. Otherwise my DI's clip like crazy. You may want to get a DI box with padding on it to help out.
