and the gear box plug in with a toneport
I assume you're using the Toneport UX2 (since you mentioned phantom power)???
If so, plug the mic directly into one of its mic preamps.
When recording, you generally want to use the shortest electronic path possible.
If you're using the UX2, the external mixer is redundant in this scenario... and is doing nothing but messing up your gain-staging (adding noise).
BTW, Get a healthy signal level by using your mic preamp's gain knob.
Then, use Sonar's track volume to control the relative volume of the track as a whole.
The gain on the Gearbox compressors is really meant for make-up gain (post compression - to keep levels consistant).
Don't expect your first recordings to sound like a record.
Having the gear is but the first step.
Listen to commercial recordings that you like... and try to get your tracks/mixes to sound similar.
As a general rule, try to get the sound as close to right/perfect as possible up front. That makes mixing a whole lot easier!
You've got a lot of learning/experience to absorb.
Enjoy the process...