cheap simple DSP crossover

best option is a board with ADAU1701. depending on other options like power-on click supppression, wide range supply input regulation, connectors, monitoring , volume control, cost will go up. cost of real time parameter change is 80$, or off line programming using an arduino. checkout freedsp board...
 
the cost problem is in the software. Analog devices does not allow the sale of their products and freeware software and have the end-user reprogram the DSP. That's why minidsp had to develop their own software . I estimate the board material cost below $30 in quantities. you have to sell a lot of units to earn back the software development.
 
so fixed XO freqs, and corrections ?
then you can save on the programming connector and just plug in a programmed eeprom. and do the development on an evalkit or any board like the freedsp board. what power supply do you think of ?
 
the DA3066 seems to have an ADAU1461 as the Mclk is driven at pin 2 from the 12.288 oscillator. the rsr232 is on uart level RXD/TXD, so need a USB to rs232 RXDTXD converter, a few bucks on aliexpress. also these guys circumvent the EULA agreement by having theyr own SW control the dsp instead of using the sigmastudio.