The TwinTrak and TrakMaster aren't all that bad, they are very clean and clear...but as stated before, thin. You have to work with the signals to make them fuller and give them body. If you're willing to mess with it a bit, you will have a good pre, but if you're new...I wouldn't recommend it. The RNP is great, but out of his price range.
The OctoPre is a great peice of equipment. I use it in my mobile live rig that I use to record band's live shows. It's clean, and great comps on each channel.
The pre's on these units compared to the 001 and 002 aren't fair really. The ones in the 002 are really good pre's. Very clean. I wouldn't even try to do a TwinTrak vs. 002 comparison...not really the same league. The M-Audio pre's (since being bought by Avid) are really not bad at all. Especially for a beginner engineer. They are, as described by an M-Audio rep, a step down from the ones in the new MBox, which are awesome pre's.
But, like another poster said, a Behringer or other low end model/brand would be a great thing to start with since they suck. Plain and simple. With what I've worked with so far, the Behringer stuff is absolute rubbish. Now I'm talking about Focusrite Red and ISA series pre's, Avalon pre's, Grace pre's, Crane Song pre's, Pendulum Audio pre's, SSL pre's, API pre's....Behringer sucks compared to those (of course). However, when you work with crap, you learn ways around it, you learn how to make it *sound* like it's a decent pre. That way when you upgrade to something better, it's a million times easier to get the sound you want. That's how I got started years ago. I worked with a mic into a POD when they *first* came out, and then I got into recording and bought a Mackie 8 channel mixer and some SM57's. Then I got an MBox. Then I sold all that and got a 002R and started my mobile live rig. Then I got a 002 for home. I've come a long way since my first recording, and some of the stuff I did with that POD will make you wonder how I did it, heh.
I'm rambling. Sorry. Point being, M-Audio should be fine. Good luck and hope to hear some clips from you soon. I always love hearing a young engineer bloom,
~006