Online Mixing

Hello frnds!

I need help regarding Professional Capturing Card!

I am currently using AVID LIQUID STUDIO for capturing and offline video editing..

But, I need some setup for online mixing.. (on the spot mixing {adding effects, trasitions} videos from 3 or 4 sources)..

I just had a query.. Is there some hardware which can be connected and used with Final Cut Pro for this online mixing?

Also, pls. let me know some other way to do online video mixing..

Thanks!