I have a Silque with 165 cranks. I do not have Di2, but the LBS wanted me to try it, and there was no conversation that this couldn't be done. It depends what level Silque you are getting, I suspect. My bike was built to order (SSL level); it did cost a lot more than the price you are quoting, but I think that you can probably still get this, no matter what. Work with your LBS, not Trek directly.