US Robotics Courier modem would be able to do 56Kbps I bet. I used it in Russia in the 90's on the shittiest landlines imaginable, it's the only one that _really_ did the job.
The problem with 56k is that it worked by having specialised hardware on the ISP end for the modulation that made those speeds possible over a phone line. As far as I know, no consumer modem can really do that, so you’re stuck with 33.6k or worse.
That was my best modem. I went from 1200 unusable to something much more usable 9600 and 14.4. Then I had the 28.8k for a few years before I was blessed with 56k. I got cable modem after that.
