Yes, one encoder taking a feed direct from your board can create a
stream that is feed to a server running Windows Media Services (WMS).
Your listeners would connect to the machine running WMS and receive the
stream from it, not the encoder.  The WMS box works something like a
splitter or 'DA' for streams.

If you wish to server multiple bitrates to your listeners; 96k/2ch for
folks with cable modems, 32k/mono for dialup users for example, you'll
need an encoder instance for each bitrate.  For audio only applications
this is easily done on a single PC with multiple sound cards.

For your application I would suggest investing in a pro quality sound
card that will give you balanced inputs.  Some can also do
limiting/compression/etc in the hardware.

WMS is a free component, although not part of the standard install, of
Windows 2k3 Server.

Hope this helps.

T.