I have been using HostGator to host all of my websites since 2006 and they have been wonderful.
You can host unlimited domains (yes, all of your 20-50 domain names), unlimited bandwidth, and the live chat tech support (it has really helped in the past), all for $14.95 a month.
Definitely one of the best hosting companies on the internet! Oh, by the way get the business plan it gives you unlimited control.
