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
That's a lot of questions Steve. You might want to break it down into different posts.

The Dalis are excellent speakers but they are designed for music. They might work well for home theater but I really don't know. They have a warm, easy to listen to sound to my ear, if that's any help.

How high up in the bass can you cross over your subs? With 2 13 inch subs you might be better off getting a pair of good monitors. They might be easier to set up and move around depending on the listening situation and could be cheaper. The Dalis are large, heavy and not easy to ship. If you bought a pair and decide they aren't right for you, you have a major job shipping them to someone else.

Dali Makes a monitor, the 300, there's a pair of them for sale on Audiogon now.

Anyway, I would start by finding a speaker you like and then work back along the equipment chain from there. If you get the 300s and like them but decide you want the full range Dalis you can use the 300s for surrounds. Or you may decide you don't like the Dali sound. Then the 300s would probably be less costly to resell.

I hope this helps. I think you'll be better off breaking this project down into smaller pieces. I'd start by getting a set of speakers you like.
If you're really like movies...

Suggest purchasing Dali Helicon 300's--since you have a 56 lb beast of a center
channel. If you purchase the 300's, then you can upgrade to Anthem AVM 50v
or Arcam AV888 as an option.

For two-channel music the 300's will sound great with the 2 fathom f113.
The ribbon tweeter combo really gets the details right with the right amp.

These are really great suggestions. I really appreciate the help. I never thought of doing monitors. I originally was going to stick with axiom m80v3's for my mains but to be perfectly honest I am really drawn to the way the Dali helicon 400's look. I am assuming I will like the way they sound better also but I suppose that is pretty subjective. Either way I will take the monitor thought into consideration.
I auditioned the 400MKII's about a year ago. They struck me as being lovely speakers excelling at reproduction of voices. I thought they would be ideal for opera lovers. Very good with orchestral music, but they did tend to congest at higher volumes. That aspect left me wanting to audition the 800's which I assumed might handle higher volumes better. I did not get to hear the 800's so I can't comment on them. The 400's are visually stunning, and are not demanding with respect to placement. I think they would be pretty good in a home theater set up. I would never buy speakers without an audition, but if that is not possible, I'd say give it a try.
Brownsfan, the congestion you heard may not be the speakers, it oculd be the preamp or if CD source the dac section unless you really know the equipment you auditoned them with. I agree with the looks and sound you mention otherwise.

Happy Listening.
You are correct on the congestion. For what its worth, at some point I may pick up a pair of used 400's for my home theater. I really did like them, but at full retail they are no where near the speaker the Magnepan 3.7's are, which is what I went with for my 2-channel system. The maggies won't work in my den though, so I could be very happy with the Dalis. There is a lot to like about those speakers.
Yeah I hear ya when you say never buy speakers before auditioning them. I am pretty nervous about buying them and the possibility of not liking them. But I hear really good things about them and the sound most people describe is what I enjoy. Worst case I audition them in my home and if I don't like them I resell them and use my axiom m80's. Thanks again for the help guys!! It's appreciated

One side note. Do you think it is unwise to run axiom center and rears with these dali's?
I think the rears could be ok, not so much the center.
Steve the 400's will be great. Matching center channel would be optimal.

Listened to 400's with 70 watt simaudio integrated. Killer sound!!
Good midrange and bass extension. Since you have 2 subs you can set the
frequency a bit higher than 400's 36 Hz.

Ultimately the 300's worked for me but 400's are easy recommendation.

Sent from my iPhone
Thanks so much Lapierre I think that is going to be the way I end up going.