I would think that latency would be a real reason to not do that...In live sound, you have to make tweaks on the fly, in real time.
Added to that, there's the general live sound mantra: "Keep it simple...." And although Line 6 doesn't list that model in their current line-up to check it out, I would bet that it really isn't designed or built to be reliable in a situation where you're tearing down and transporting the gear. And then there IS the issue of connections:
Are the outputs balanced to run long cables without picking up interference? Probably not. Is the operating level of the box designed to have the headroom to run live sound? I'm betting "no" on that one, too.
Please trust that I am not bashing your obviously nice computer rig...but live sound and recording, while the 2 can share many similarities, are really 2 different aminals.

Thanks Moonbaby. I really appreciate your thoughts.

Yeah, the UX8 is discontinued. You're right, it's not built very tough, so I would have to be careful transporting it. But this wouldn't be a regular thing, and I have a nice gator case for it.

How can I tell if the outputs are balanced and about the headroom? I don't really know what that means.

If nothing else, this will be a learning experience, which I am always looking for, lol. Thanks for walking me through the thought process.

There are no balanced outputs on the UX8, and the operating level is too low to drive power amps for house or stage systems. It was not designed to be a live sound mixer...period. I am leaving my job now - Isaac's outer rain bands are roaring towards us. I will continue this tomorrow. Meanwhile, do some investigating about LATENCY and how it will affect live sound oproduction. Later...

[[url=http://[/URL]="http://line6.com/le…"]Legacy Products | Line 6[/]="http://line6.com/le…"]Legacy Products | Line 6[/]

According to this page, the outputs are balanced. But I still don't really understand what that means. :/

I need to clarify that there are no balanced MIX OUTPUTS... there are NO MIX line level outputs of ANY type on that box!!!! You do have a couple of headphone jacks, that is your only way to get a feed to an outside destination that is a combination of the sources that you plug into the box. THIS IS NOT A HARDWARE MIXER!!!!!!!
You can take the (8) "balanced" line outs from the individual inputs on the box and connect them to an outboard mixer and use THAT as a mixer. But using whatever software mixer that may be inside the Line 6 will not really work for live sound because of the inherent LATENCY of the system.
And, in a nutshell (because I can't write up a description better than what can easily be found if you Google'd it) "balanced" lines are used to minimize noise interference being picked up by cable runs that are longer than say 20 feet or so. This is very important in any sound gear but especially in live sound where interference is a major issue. Connections are usually via XLR or TRS plugs. They are 3 wires (Hot, Cold, and Ground) as opposed to 2 wires ("unbalanced" - a "Hot" and a combination "Cold/Ground"- like on an electric guitar ). This is determined by the internal circuit design, not just the wire configuration. All of this is pretty much moot, though, because your box is designed to take analog inputs and convert them to digital to be processed by the computer. The LATENCY (time delay) in that system is going to thwart your attempts at mixing in real time.