54mbps is sufficient. But that isn’t the speed of your internet connection when streaming to remote. It’s the speed from within your local network.
320kbit/8 equals 40kb/s. That is the actual speed you need to flawlessly stream a 320kbit mp3.
Try visiting speedtest.net or something similar if you don’t know your upload speed from home.
Though the 2-3 minutes to play a song worries me. How could a single request take so long, and eventually work. I’d more likely say your home firefly could not be reached. But it eventually worked, so that’s clearly not the case.
I don’t really know how fireflyclient works. If you have a real slow internet connection at home, maybe the 2-3 minutes before hearing anything was the program trying to fill a couple of buffers. And after that, the bandwidth stayed insufficient so you hear gaps all the time.
That might be a possible explanation.
Also, as you’re saying you know nothing about port forwarding, how did you get it to work from remote in the first place?
Routers block any incoming connections from the outside world, unless you forward a certain port to a certain PC in the local network.
So you must have correctly forwarded the port on your router to the PC with firefly. Else it wouldn’t work in the first place from outside your local network.