Sony TRV350 - Recording audio

I have the following hardware:

Sony TRV350 - Using firewire to record straight to my PC.

M-audio firewire solo - As my soundcard.

Rane TTM-57SL stereo mixer - running into the firewire solo.

What I would like to do is record not only the video but audio directly, instead of from the built in mic. Since my soundcard is already using its balanced and unbalanced ports, I assume its a no go to run anything to it.

Would this mean I need a mixing board?

I tried connecting external mics to my TRV350, making sure to use the correct balance ‘power’ mics, but the result was so-so and sometimes the connection crackled.

Why not just connect a couple of good mics to your Rane mixer and use that feed for your recording ?

Nick. . .