We ended up with a Broan 'Power Pack' with an external blower. (see link below photo) We had the upper cabinet constructed with a center channel for the duct so we could still have shelves on each side, plus the duct is covered so it looks great.

The results are mixed. On the plus side, the appearance is great. The Broan Power Pack (the part that installs in the cabinet) it only four inches high, so it eats very little cabinet space, and it uses just an eight-inch duct, so the channel width is reasonable. (Need a bit extra width in the channel so the installers can tape the duct connections.) With the cab doors closed, everything is covered up. With the doors open, it looks clean and we get the convenient shelf space. And with the 600cfm blower, cooking odors get sucked up nicely.

But there are negatives. One is that the Power Pack is cheaply made, but what should you expect for a mere $400?!? (We would have spent more on something nicer, but neither Broan nor anyone else makes something similar with better quality.) Both the fan and lights are controlled by flimsy plastic sliding switches. The housing and the decorative cover bend out of shape easily. And it's difficult, if not impossible, to get the decorative cover to lay flat against the bottom of the cabinet. (Spent only an hour on that issue so far...hoping another 2-3 hours will get it to fit right.) The remote blower (another $400) is in the attic just above the cabinets. I think the installers had never installed a remote blower. They have it sitting right on the joists so some vibration transfers to the cabinets. In the upper cabinet just to the right of the vent hood cabinet, and right below the blower, are drinking glasses. If the glasses are touching each other, we hear the tinkling sound of the glasses vibrating against each other when the blower is on. Separating them fixes the problem. The blower is a bit noisy, but not excessive. But, in some parts of the kitchen you hear an annoying low frequency noise. It's weird. You don't hear it standing at the cooktop, but three feet away you do. The installation instructions include an option to hang the blower from chains attached to the roof supports, which might have addressed the issue. I'm thinking of putting some sort of rubber-like material between the blower and the joists to act as shock absorbers. The point is if you get an external blower, think thru where and how it's mounted.

(Note on photo: Backsplash tile is, literally, on a slow boat from China...was on backorder for 2-1/2 months.)

Here is a link that might be useful: Broan Power Pack