Miele's used to be a high quality vacuum but those days are long behind them. They have a lot of aggravating shortcomings such as a short but ridiculously stiff hose that fights you, tries to kink ( and often succeeds ! ) and sometimes flips the canister over, really small low quality standard attachments ( the standard Miele dusting brush is an insult ) and a treacherous and temperamental bag dock that is often hard to get the bag seated in correctly resulting in leaks, and their bags have a spring loaded flap that pushes the bag back from the lid causing a big dust leak. Kludge! Then price their bags and filters. Nein, danke.
Sebo canisters are not as powerful as Miele but are a lot better made, vastly better attachments, a much nicer hose that is around 8 feet long compared to the pinche miserable 6 footer for Miele. Nicer to use in every possible way, but Sebo prices are simply ridiculous. The retail price difference between the E and D model canisters is around $400, but I doubt it cost Sebo even $10 more to make a D compared to an E. They just bone you on price, Miele too, because it says Made in Germany and they have Americans bamboozled into thinking anything German is automatically and naturally better. In Europe Mieles are just another vacuum sold for a third the price they sell them here ( and that was before tariffs ) and Sebos aren't even available in a lot of European nations. If you can get a low price on a K that could be a good value for you.
The Nilfisk thing is nothing special and no power nozzle for your carpeted area. Pretty sure that same vacuum is sold under other brand names.
The Aerus Classic and Aerus Legacy are both mostly made in the US, final assembly is in Virginia but components come from abroad. If you can find an Aerus dealer willing to sell you one of these for under a grand you will get a fairly quiet vacuum that ought to last decades. Aerus now sells really good four layer synthetic HEPA Style C dust bags and they have an activated charcoal pre motor filter. The design of the Classic dates to 1984 though motors have changed over the years and they have gone back and fourth with having a suction selector or not. The design of the Legacy is based on the Classic with a different upper body with attachment slots, a different hose and wands. Both come with an outstanding power nozzle and to me one of the industries best hard floor brushes. The only drawback is that some Aerus dealers are greedy and dishonest. But if you can find an honest one willing to sell you a Classic or Legacy for under a grand that would be a really good value. The Guardian Platinum is gorgeous looking but oh so fragile and hideously over priced. Don't even bother with it. I have one but I have to baby it because the plastic bottom housing and bottom of the bag chamber are much too thin and easily broken. The whole vacuum is fragile while the Legacy and Classic are thick, solid and durable old Electrolux USA designs that just haven't changed much over the decades. Some like that, others do not but worth a look.
You say you want quiet so that has me not recommending my favorite canister vacuum, the Kenmore 600 Series and specifically the purple 81614 flavor of the 600. It is not as quiet as a Miele or the two Aerus I mentioned but in terms of what you get for what you are paying there is nothing better on the market today. I have Kennys going back to the late 1940s and have had an example of pretty much every one of their designs apart on my bench to refurbish for my collection. The 600 is easily the best made, best materials and workmanship and the most thoughtfully designed canister vacuum Kenmore has ever sold. I have Kenmores from Birtman Electric, Whirlpool, Singer, Eureka, Panasonic and LG. This new 600 Series made by Suzhou Cleva Electric Appliance Co Ltd is the best Kenny ever. Compare the Kenmore dusting brush and crevice tool to the crap Miele gives you. I don't think any modern vacuum has nicer attachments and none of the megabuck German vacuums sold here have an electric motor powered upholstery brush like the Pet Powermate. SO much better than an air driven turbo tool ( incidentally Aerus has an electric motor driven upholstery brush too, the Sidekick ). I don't find the Kenny objectionably loud but everyone is different.
Last, you could do a lot worse than buying a clean used Tristar A101. There is an optional 12 foot long hose for the modern Tristars, the power nozzle motor, brush roll and belt are the same ones used by Aerus. The wands are identical to those used by the Aerus Guardian Platinum. All stuff that is still in production. They are all metal bodies, an aluminum-magnesium alloy called Magnalite, that you would just about have to drop off a second story window onto a concrete patio to break. I have a 1944 or 45 vintage Compact Model 1, the very first vacuum they made before changing their name from Compact to Tristar sometime in the 1980s. Still runs fine. They are super simple machines and about the only things you might wear out are a motor eventually ( easily repaired or replaced ) and maybe the hose. Three screws, a little prying and the body is apart. Simplest modern vacuum I can think of.
A clean used Miracle Mate has the same virtues as a Tristar, very similar design but M-Ms are heavier due to an internal cord winder. On Tristars you have to manually wrap the cord around the vacuum body, but the cord is long. On M-Ms they have a retractable cord, but the cord is not as long as a Tristar cord. M-Ms have nice hoses and attachments, use high end Sebo or Lindhaus power nozzle and are pretty quiet. The bodies use the same alloy as Tristar and are equally durable.
