one thing to consider about the cal 15. it does not have a digital out. it cannot be used as a transport. i have not heard the audiomeca obession so i cannot comment on the sound between the two. i did own a cal 15. it does need a pre amp to sound its best. the digital gain looses detail at low level. it also is very detailed...a little to much for me. i went with a birdland dac and trans (old pioneer dvd). to me much more musical. dac new is about 800$ you should be able to find a used cal for same price. i would go for the cal tube dac and trans if i were going to go cal. i have seen some good buys on agon. imo.
good luck jim