A "newsreader" is the client software that you run on your computer to read Usnet articles. "Agent" and "Gravity" are examples of "newsREADERS".
A "News server" is the thing in the cloud that the news reader connects to, to serve the articles to your newsREADER. Most newsREADERS are free, with the obvious exception of Agent. News SERVERS include "ThunderNews", "GigaNews", "Individual", and the one run by the makers of Agent, "Agent Premium News". Individual is cheap, about $14 a year, though doesn't have binary groups. ThunderNews is around $7/month, IIRC, and APN is $3/month for 15GB. *ANY* of which is better than Googlie Groups.
You don't need to upgrade. There are many other free news readers, as well.