In reply to Jaris84:
Ok, thanks for the answers so far. The problem is that depending on where I read, i varies who is the warmest. I would assume more down equals more warmt, but then again, maybe the technology behind each bag has some impact as well.
The summit 800 is normally priced higher than ascent 900, although now on sale, it has a bigger discount and for me it is cheaper than ascent 900.
On rabs own pages, it says the summit 800 is warmer than ascent 900:
http://rab.equipment/us/ascent-900 , even though the temprating says otherways.
I am very confused :-P