I know I used JRComm a lot back in the day...
I'd give it a shot.. Although I can't remember off the top of my head how well it handled IBM ANSI.... Very nice ZModem support tho..
desiv
Both NComm and JRComm should support IBM ANSI _if_ you have the IBM ANSI fonts on your system. Well, that's what my hazy memory tells me anyway. It has been some time since I used a terminal package.
Also, you can grab xpr modem libraries for the different transfer protocols out there as well as replacement serial.device which should allow for faster transfer rates on an Amiga compared with the system supplied one. Unfortunately, the standard UART Amigas used are not very fast which is why so many people used to get serial cards.