If you go with SPI look at this thread. SPI is different on the ARM chip
http://forum.arduino.cc//index.php?topic=157203.msg1424519#msg1424519
I know its more about slave mode but plenty of tips for DUE SPI in there.
If you can use the Due 12bit DAC all the better.
Can you not use a pair of resistors to do a voltage divide and then a bit of math on the output to scale it to what you want.