If you have any interest in canister vacuums then I HIGHLY recommend a Hoover Celebrity canister!! You could do a power nozzle or straight suction but a power nozzle will definitely show you the machines full potential. Great sounding, very powerful, large bags, high performance, very durable, full array of great attachments. I love them!!
I used to use one semi-commercially and in the same environment where Panasonic uprights and Kenmore canisters had lost airflow from the extreme dust of that environment, the Celebrity was still going full throttle and despite no HEPA filtration available. I have never had an issue running a Celebrity and my dust allergies are bad.
Rainbows and Filter Queens are neat if you can find them at a good price. With a Filter Queen it's a toss up. I find the newer unit has a stronger suction unit, but the older units have a stronger power nozzle. Rainbow the newer ones have a really great power nozzle due to the headlight, serpentine belt and street sweeper like brushes some of the others are cool finds too.
A Hoover Convertible/ Decade machine is really impressive to use. They are not all created equal either!! Different motors, different bases, you can surely find one that fits your tastes better whether it's sound, color, metal, plastic, cloth bag or vinyl bag. Any Convertible or Decade that will take a Top Fill type A bag, you would have the option of using a HEPA A bag.
Hoover Elite style machines are quite impressive. It could be branded: Dimension, Legacy, Elite, Sprint, Spirit, Decade, Convertible, TurboPower 1500, 1700, 2200, Elite, Encore, Runabout, Futura. There were many. You could choose depending on color, headlight, attachment set, soft bag or hard case, etc.
Kenmore/ Panasonic canisters appear often on Craigslist or in thrift shops. Generally very powerful suction units. With power nozzles you might get lucky to find one with the headlight equipped 12" head which despite its flat belt design, it was a great performer. There are many models and generations to choose from. Generally the rectangular bodied ones are better made. There is a green colored Panasonic one on eBay for $60 currently.
Of course the more you stumble into thrift shops, flea markets, estate sales, yard sales could surprise you one day with something quite interesting such as a Royal upright, Royal Tank canister, Filter Queen, TriStar CXL, or perhaps even a bargain priced Kirby G6 which I think offers one of their better color schemes.
My collection is primarily canister vacuums-- all of which have power nozzles because a brush roll is my favorite part of a vacuum. None of my machines are plain white and I don't do much with browns. No pinks here. I have 1 purple and it's probably going to go up for sale. All of my units have to meet my performance expectations because they all receive use whether in my home or at work.
I have to be able to use the machine without an allergy issue, which I've found eliminates my ever using another Oreck upright. I've used about 15 in my life from the Commercial Dual Stack, standard commercial, XL Ultra, XL 21, swivel head model and had allergy spasms within a few minutes of using every single one!!
So with that in mind, keep an open mind. When you get the chance to meet other collectors or go to store that allows you to try a machine then take it for a spin. Each has its own attitude and sound. I love the sound of many. Others like the new motor that Sanitaire has come out with for their SC886 and many other models drives me nuts and I'm definitely not a fan. It's not that it's extremely loud cause it's not but it's the tone makes the head ring; and I'm only 33 so I can't imagine how it hits some other generations. I also love outdoor power equipment such as commercial gas powered lawn mowers, string trimmers and leaf blowers so it's not the volume, it's the tone that gets me. I love a nice loud commercial weedwacker!! A Kirby G series in attachment mode hits me the same as the newer Sanitaire motors. Just not a machine for me!!