These are high numbers for the 1.74. I have around 300kB/s download and around 70kB/s upload.
My upload rate stays low on the 1.102 and 1.116 version, around 75kB/s
I might have some insight to this upload performance issue. It's called Delayed ACK in TCP. Modern IP-Stacks send data all the time and expect that TCP segment acknowledgement might come late. On Amiga, most IP Stacks (notable exception: RoadShow) will wait for the actual ACK before sending data again.
This is a behaviour of the remote machine which must be circumvented there. Examples:
OSX (commandline): sysctl -w net.inet.tcp.delayed_ack=0
Linux (Samba smb.conf): socket options = TCP_NODELAY
Windows (not tested by me on recent versions, Registry):
find your LAN interface there and add the following keys: