I showed the MOSFET driven resistor array earlier and while searching for digital potentiometers I found 2 that are SPI based on 10K. One is the MCP41010 with 255 steps, but the one I really liked is the new AD5231 with 1024 steps. They exist in 10K, 50K and 100K versions and provide a far more elegant solution that a discrete array of MOSFET’s and resistors.
AD5231 cost ca 4.- USD, but it contains memory for power up, support both 3V, 5V and +/- 2.5V and a lot of advanced functions. I have a few analogue designs I want to dig into with this, an analogue PSU is one of them.