That's a little vague. Any four channel interface will do. What kind of show, what kind of music, what kind of hall and why do you need re amplification?

Sounds like your best bet is a mixer to send 4 bus groups into a 4 channel interface. Need more detail to give a more specific answer.

olin

OK...2 guys on stage, 2 guitars, 2 mics, thats the 4 chanels
I'd like to record the 4 chanels at the same time separtly so I can do some valume ajustment to any of the tracks later
and at the same time minamize the audience sound.

I say minimize audience sound when they are talking trash LOL, no actually keep that. In a live recording you totally want at least one set of room mics. Why? so you can hear the clapping, banter, cheers, room's acoustics.
Not sure if guitars are acoustic or electric or both. You sure want separate inputs for your DI, and mic lines. Plus the two vocal mic lines. Your going to want the control later, unless this is just a quick demo. Get a couple splitter boxes, 2 sm 57's, and an 8(at least) channel mackie mixer, + an interface, of which there is alot of talk about on RO. This allows you to have some nice DI'd guitars, real ambience from the room, clean vocals, and perhaps some efx that you send to the house but not your recorder. A mixer w/ direct outs such as an allen and heath or mackie, will give your interface all the dry feeds, and allow you to mix any way you need to get the sound to the audience properly.
If you question how to get the room mics 'out of the way' put them near the mixing board, or at the bar (with permission), or hang them out there. Listen to your favorite bands' live recordings, the audience is clear as there. It doesn't sound weak or phasey, or distant.

If your board doesn't have a direct out, split the signal with a splitter box or patch bay. Send one signal to the board and the other to an interface with preamps.

Unregistered, post: 361610 wrote: OK...2 guys on stage, 2 guitars, 2 mics, thats the 4 chanels
I'd like to record the 4 chanels at the same time separtly so I can do some valume ajustment to any of the tracks later
and at the same time minamize the audience sound.

To give you full advice, we need to know the make and model number of the mixing board. It would also help to know whether the guitars are acoustic (with mics and/or pickups) or electric (with amplifiers). If they are electric guitars with amplifiers, what are the makes and model of the amplifiers, and is it just the vocals through the PA or are the guitar amplifiers put through the PA as well?

Several questions, but knowing the answers to these helps us narrow down the recommendations for you.

OP are you the one supplying the sound support as well?