AmIRC is the best IRC client by far. Here are the requirements from the guide:
Hardware
--------
AmIRC was written for the Amiga family of computers, and has been
tested on Amiga 500, 1000, 1200, 2000, 3000, & 4000 computers in various
configurations.
Software
--------
AmIRC requires MUI V3.6 or later in order to run.
AmIRC requires KickStart & WorkBench 2.x or later, with setpatch 40.16
installed.
AmIRC020 requires a 68020 or higher CPU and OS3.0 or newer. This
version is optimized for such machines.
If you plan to run a TCP/IP stack and AmIRC among other Internet
applications you should have at least 2 megabytes of RAM.
Maybe you are trying to run the 020 version or you have some MUI classes missing.
