Dali 400mkii or 800mkii?

Hello, this is my first post on here so please bare with me. I am piecing together my new theatre system and have a few questions. My room is roughly 14x25x9 feet and I am thinking of running either the Dali 400 mkii or 800 mkii. I currently have a theta dreadnaught gen ii and have access to either an onkyo processor or lexicon. I have an axiom vp180 center and qs8 rears already and 2 fathom f113 subs. My questions are 1) would the 400 or 800 be better for my room size 2) do you think my axiom center and rears will sound bad with the dali's? 3) am I shooting myself in the foot running an onkyo processor with this setup? 4) does anyone have suggestions on alternative choices? There are no places to demo higher end speakers where I am so I am basing a lot o my decisions on what I have read which I know is not necessarily a good thing to do. This will be used for 60% movies 40% music. Sorry for the long winded post. I really appreciate any help