amidi -p hw:X,X -s hurtz.syx 
 Ahh ... X,X does the trick, right? Thanx! 
 
 No it does not. (But it would have been really nifty if it did ...)
 You meant to say that if I use --help, I shall see that -l will give
 me a list of devices, which I should then shell-replace in the script
 traversing through all possible midi-ports. 
 
Wokrs for me, replacing the X by the desired port, e.g.:
amidi -p hw:0,0 -s sysexfile.syx
AFAIR, the port must not be occupied by any ALSA connection, so first
you should disconnect all other MIDI connections.
Best regards
    ce