We are remodeling our kitchen, and installing a new 36" gas range. We are looking for a built in range insert. I currently have a partial run of 6" duct vented through my roof however i will have to do some modifications on this anyways as its location will require me modify my ceiling slightyly.

If I upgrade to a 8" or 10" duct this would be relatively miminal work (new roof vent, new duct) however likely within my diy wheelhouse.

I went to a local brick and mortar and they are pushing the Zephyr models specificaly Monsoon 1 and 2 which would run be $1149-$1699 before taxes. I heard about Hauslane and their In-R200 would run me $570 and has an equivalent CFM of 840, and I can run this to a 6" duct which is already in place for me.

What am I missing here to not go with Hauslane? Is there marketing gimmicks and you cant run 840CFM in a 6" duct or somethign along those lines?

No objections to the CFM & 6-in so long as you have Make-up air to supply their brags about suction (read their caveat ... window open or closed).

Our home is about 20 years old, I wouldn't imagine it's sealed up so strong as to need this or is my assumption probably wrong here?

Read this first before you decide.

Range Exhaust Hoods are critical:

https://bamasotan.us/range-exhaust-hood-faq/

840 CFM is lot of air volume for a residential vent hood. Are you really gonna do that much smoky cooking? If so, for that to work, you'll need to do as the guy said and open a window or a door when you run that thing. This provides what's called make-up air because it makes up for the air you're pumping out of the house, 840 CFM. If you don't provide an easy path for make up air, the vent hood merely creates a slight vacuum or negative pressure in your house and probably won't really move 840 CFM out of the house.

Its probably the spec for that vent hood.

We install that large and bigger in residential homes all the time. Just did a 1200 last week.

To the op, as posted above, you've got to provide make up air. Sometimes, you need a electric damper that is tied into the hood. Sometimes you can get away with a pressure damper.

Check on the sound ratings for the range hoods. Generally, it was the lower you went in price, the louder they were.

We have an island range hood, so we on the more expensive side since it was so visible (needed to please the wife) and I also wanted it to be quiet enough to talk around. Futuro Futuro had some of the quietest ones and had a style we liked (Minimal White). Built in would give you a lot more options but definitely pay attention to the noise ratings.

This is what I was going to say.

We had a Zephyr monsoon after a remodel in our last house and it was extremely quiet. We even turned on a feature to just run once every hour or two and could never tell.

Our new house has a cheaper hood (don't remember the brand) and we have to turn the volume on the TV up when it's on even the lowest setting. And this isn't a completely open floorplan either. The other negative of this one is the grease traps. It's not as well designed or sealed as the Monsoon was so I have to clean the filters about 3x as often or it'll start dripping.