I currently have an avantone ck-1 and am thinking of upgrading to the Sennheiser MKH-50 (wanted schoeps but I live in Seattle---humidity can be a problem).
I have a mix pre d + marantz 661 that I'd connect the mic to.
The main reason is that the avantone does not have a good reach--i find that it needs to be fairly close to the subject and considering i film, I'd prefer it to be further away in interior shots. I have a rode ntg3 for outdoor use.