Hi, Lee and Brian!
I'm responding to Brian here because although I agree with alot of what Brian is saying I would have to disagree with the mic choice for a couple of reasons, although I do own the mic myself and think its 'ok' in certain cases.
1. The DS70P is a stereo mic and your input is mono and the way axis treats stereo mic ins is to discard the right channel. So you are paying for 2 mics and using one.
2. The pickup pattern is uni-directional stereo, not ideal esp. if only one side works. If you are looking to pick up a speaker from a distance, you want a more directional mic (think football sideline mic, not quite but same idea).
The primary issues with speech clarity are going to be mainly dealing with reverb wash. A sound survey would identify the best placement of the mic and suggest the optimal setup, tho a couple basic rules wil always be true.
Use a highly directional mic, like a shotgun mic if it is in the budget.
Avoid the corners(unless using a boundary mic); standing waves create various frequency build-up called modes which are worst in the corners.
Use a low-cut filter or a mic with reduced lf-response.
You say there is no total mix you can tap, but I assume there are speakers which amplify at least the voice component?
One effective, although admittedly low-tech, idea is to simply setup a directional mic three or four feet pointed directly at the cone of the speaker. This will enhance your audio stream quality greatly!
One mic with which I have direct experience with Axis is the Sony ecm-cz10, its super-directional and works great with speech. It also comes with a shot-gun like tube that you'll want to use.
P.S. I'm assuming that its not possible to use a wireless lapel mic here(best), also you could get the stereo mic and get a y cable to combine the inputs, tho im not sure how it might affect the phantom power...
There are other things that affect audio quality(codecs, vbr etc), obviously, I'm just speaking to mics and placement.
Let me know if you have any questions.