I use Linux/Darkice to do my streamings. I use an old wyse termianl VX0 I picked up on ebay for $25 and the OS is installed on a 2GB flash drive. For audio input I use an iMic made by griffin I also got from ebay for $8. With alsa you can then use the dsnoop plugin and split the stereo input in to 2 feeds and run 2 instances of darkice with different configuration files. Just google "Darkice split stereo input" there is a google code post with all the info.
If you can boot your laptop from an USB flash drive, I don't see why you couldn't do something like I am doing. Mic inputs on computers are made for electret mics (there is a phantom voltage to power mics of about 5 to 8 or so volts). This causes all sort of hissing and humming noises and what not if you are connecting scanners direct without and impedance matching / isolation circuit in-between.
I imagine you could add more iMics or similar devices to increase the amount of feeds. each time adding 2 feeds or more. You can listen to my feeds at TRYON Amateur Radio Club K2JJI - RACES Drill – Tuesday at 7pm EST | On air: -146.70Mhz PL:100Hz | EchoLink: 510372 | Fulton County NY