No such thing as too much suction !

The most important thing (to me anyway) is the proper and efficient design of the piping system. That will make the biggest difference.

You don't mention whether you are going with an electric brush or an air driven one. More flow needed for that. Are you going to be getting something like a hidden hose , which will require a specific pipe layout or a large amount of in wall space depending on which type you go with.

Vac Pans are really handy if you sweep your floors.

You should also read up on whether you want a filtered unit (like that elux) or a unit that takes bags (nutone, airvac) or a cyclonic type (drain vac, imperium, vacumaid)

I'd think long and hard about where you'll use and need inlets or vac pans based on your furniture and cabinetry plans. The Pipe Hangers will just wing on install day if you don't a have a blueprint.

Xedos you are the man as you are literally knowledgeable about every subject on this forum. Will be using electric attachments and prefer filtered over cyclonic and bagged although many filtered like the Electrolux can be converted to take bags fairly easily.

If you're venting it to the outdoors there's no reason to get a filtered vac (or bags). Whatever doesn't stick in the bucket is blown out through the wall. I never saw how the size of the house is a factor in sizing the vac but they all seem to say it is.

I have the biggest unfiltered Vacuflo (240V, 2 motors) with 2 hide-a-hoses in a small house. The dealer suggested the big one so it would suck the hoses back into the pipe with ease. There's not much of a price difference between big and little ones and most of the final cost will be installation labor. It works well.

I've had a Nutone in the past and that was quite satisfactory.

Here is a link that might be useful: Vacuflo

The house size factoring into the equations is this:

The larger that house you have , the more piping is going to be required and the more piping you have the more static pressure is created needing more airflow to overcome the pressure and still keep the dirt/dust in the airstream back to the filter,bag,bin ect...

These are simply off the cuff, back o napkin, WAG, easy to digest numbers - quickly. I've seen small to modest houses with large and elaborate pipe systems with tons of outlets, pans ect. that required larger motors.

ALso, if you vent to the outside , you need to be aware of makeup air ! If you have a new house that is well insulated and tightly sealed and vent the vac to the outside you need to replace the air you are spitting out and it will come down your hvac flue, chimney, hot water heater vent, ect... if you haven't made other provisions.

I have nothing useful to add in terms of what size to buy, but I will add a second comment about Vacuflo. I've used other systems over the years, and this is, hands down, my favorite.

I have a Vacu-Maid system I'm very happy with. Way better than the last one I had (don't remember the brand). Very easy to use, hid-a-hose, seems very well made and engineered.
It really sucks!

I seldom used my vac pan in my kitchen toe-kick. When I cleaned the kitchen floor I cleaned the rest of the house at the same time...so the vac hose came out. Unless you have messy "people" (dogs or little kids or someone who wipes things into the floor) you may not use your vac pan much. Then again you may use it every day. Depends how much you like to clean.

Only problem we had with our central vac was the handle of the floor brush. The part where the hose attached to the brush head got a short (????) in it within a year. We had to hold the hose a certain way to get the beater brush to work. After a few years we got rid of carpet so we didn't use that part any more. Had it ten years total with no other problems.