I owned a Fast Track Pro and it had wimpy sad little pre amps, so not to worry about quality as it's not really there to begin with. I'd say a Behringer compressor is a perfect match up...
I would do as Mike is saying and insert it. That is the traditional way to use a compressor on a channel strip. They are optimised to work that way.
You will need that cable =,1/4" TRS - Y's to 2x TS 1/4".
There are those who preach about not using compression on the way in,,, Myself I love it,, lt makes your lyrics understood. Don't worry about hi fidelity ,,, we lost it with the Mp3 anyways... Just make good music.