Based on the parameters that you posted, I thought "headworn mics". These are used with great success in live sound where the speaker may not have the best vocal power, they "track" the mouth so that there is no problem with head movements, and they are designed to minimize extraneous sounds (mousing, papers rustling, etc.). You see these all the time in applications as diverse as aerobics instructors and preachers.
You will, of course need a mixer. And as far as the speakers being able to turn their mics on or off, personally that scares the bejabbers out of me (being a sound mixer) because there is too much room for potential error. BUT there is a device called the Cough Drop (by Proco). This is a footswitch that momentarily mutes the mic when you press the switch down. Broadcasters use these to cough, sneeze, etc.
So now...what's your budget?
(6) headworn mics, each with a Cough Drop, a suitable mixer , cables, etc. can set you back at least $1500, and easily much more.

"there is too much room for potential error."
There's so much, I could drive a truck through the gap.

The next mics or anything that our band gets, I will either make sure there is NO switch or volume knob on it or that it's thoroughly bypassed.

One of our guitarists sometimes turns his volume down. It's an acoustic with a pickup so I get nothing cause he's forgotten. Sucks especially when you only have him and two singers (one of which has their mic turned off).

FWIW - I'd make sure to get a mixer with at least one aux/monitor bus. That way you can still make your recording and send an independent mix (of just quiet speakers, etc.) off to the "live broadcast".

Re: Live panel discussion recording... hardware recomendatio

ganast wrote: I will be regularly recording a panel discussion of 4 to 6 people .... Some participants will speak very softly, and might need to be individually mixed into the live broadcast

Is this being recorded in a 'live' format, or being broadcast live over the airwaves?

This is for radio, right?

What kind of mixer will you be using?

It is live, and it is not (yet) actually going to be used for fcc controlled broadcast, but will go direct to internet for now.

After the advice I have gotten here, offline, and [="http://www.homerecordingconnection.com/forum.php?action=view_thread&id=18465&frm=1"]here[/]="http://www.homereco…"]here[/]

I was thinking about using the [url=http://www.m-audio… nrv10 to mix either a set of Sennheiser pc-166's or something similar...

Or, directly recording a set of [="http://www.plantronics.com/north_america/en_US/products/computer/multi-use-headsets/audio-995"]Plantronics 995[/]="http://www.plantron…"]Plantronics 995[/]'s with Garage Band or Pro Tools... They are USB, so they would need to be mixed in software.

Or possibly just using two condenser mics set in the center of the discussion area... in which case, I would probably use a mixer like the [[url=http://="http://www.digidesi…"]mbox2[/]="http://www.digidesi…"]mbox2[/]

"mixer like the mbox2"

Interface ;)

I don't have a great deal of experience doing exactly what it is you are trying to do here but my thoughts are this. You definitely could use two omni directional condensers and an interface but the problem of background noise and the individual speaker volume issues will remain. I noticed in this config. you were considering the Line UX2. I think that for the same sort of money you could find a more suitable interface (unless you record guitars at home) for your specific purpose.
I would would be much more prone ( if budget allows) to head in the other direction. Individually micing each participant but would stay away from the headsets you are considering for a number of reasons. First personal comfort, wearing a headphone set up for two hours unless of real high quality is uncomfortable furthermore I think it will be difficult for inexperienced people to relate well to each other when hearing other participants isolated in a headset. The other factor is that six USB mics would require the use of some type of software mixing and I am unsure of how well or easily that would work.
So what I would consider is using lav mics like this
http://www.markertek.com/Audio-Equipment/Microphones/Lavalier-Microphones/Shure-Inc/SM11-CN.xhtml
and the m-audio NRV 10 you linked to above or something of that nature. The fact that board sends out a stereo signal via usb is ideal for internet broadcast and should not have latency (delay) issues that may be problem in using a recording interface. You will also need a decent pair of headphones to monitor the mix of the mics.
This set up will reduce paper shuffling noise etc. , give you the ability to set individual volumes for each speaker and IMO give you the most professional results.
You could as was suggested use "cough" switches to cut audio during side discussions but I think that inexperienced speakers would be unlikely to remember to use them. If you are considering any type of cut off it must be momentary (cuts mic off only when depressed, released, mic goes back on)

Cool... OK... this is some good advice. The comfort of the headsets would indeed be a problem for some... I had forgotten about that issue... Although I am an information junkie and would love to hear the live feed, it would probably mess with the minds of some of the participants.

Also, as regards the 995's, I thought maybe they would overload the USB bus with 6 simultaneous USB mics, or that the wireless signals would interfere with each other. Still waiting for a [[url=http://[/URL]="http://soundingboar…"]word back from Plantronics[/]="http://soundingboar…"]word back from Plantronics[/] on that...

I think I will go with the non-usb mics, and offer both headsets and lavaliers. I guess I'd like those who can handle hearing the feedback to do so, so that they can self-moderate... and potentially hear the other participants better.