Thomas33:
I will try it today and mail back. I m sure it'll run like hell
And it does :
   if (c == 'B') { // needs 10 to 11 ms for all 16 analogValues :-)
     char a[1024];
     for (int analogChannel = 0; analogChannel < 16; analogChannel++) {
      sprintf(a+24*analogChannel,"analog input %2d is %4d\n", analogChannel,analogRead(analogChannel));
     } Â
     client.write(a);
    }
Of course, the extra packets for the command echo and the "END" can be included too, but this whould have damaged the speed comparision.
BTW: The FASTADC stuff seems to save around 0.1 ms for each analogRead.
So I can put a SOLVED on this topic. Thanks SurferTim again!!
(Next will be moving to WLAN, but this will be a new big thing.)