I'm seeing this problem too on my new Mac Mini 1.5ghz machine. My home is wired for gigabit with a Netgear switch connecting to my D-Link DIR-855. On my 100mbit connection I top out at 0.5 mbps down, usually it's hovering around 15KB/s.

I haven't used an Amiga-like system in 15 years but as soon as I get my bearings I'll post proper HW details. :)