I'd like to point you in the direction of UltraStream
We're a very reliable streaming company... Our clients include both business and the general public.
We offer all our packages based on concurrent listeners at a full 128kbps bitrate - and we're very cheap.
You can get 25 concurrent listeners for the whole month, for just £10. Nothing extra to pay. 90 listeners is just £30, and for £50 you can stream to 150 people. That's enough for a conference.
So if you want to get started, check us out:
http://www.ultrastream.co.uk