Stan - For starters, since you say 1/3 of your condo is bare floor, do you use your vacuum to clean your floors? Or do you sweep? Or, let's put it this way - would you use a floor brush on a vacuum and vacuum bare floors?
If the answer to that is yes, then I would consider a Sebo Felix. Yes, it's outside your price range, but it's usually about $700 at most vac shops and online. So it's not too expensive for you. It comes with a floor brush attachment that you swap out the powerhead and attach. There is also a Kombi head available for it, it's a straight suction head that switches between cleaning area rugs and bare floors. For people with mixed flooring surfaces that prefer to vacuum them instead of sweeping, it's a great choice. If the price is a issue, you could always buy the Sebo Dart, which is a stripped down Felix, but you lose some features like the swivel PN neck and variable speed control.
Don't bother with the Sanitaire Eon upright Lesinutah showed in his post. Yes, they clean well and filters well, since it's a Chinese made copy of a Sebo G series upright that adds a HEPA Filter to the exhaust. It can even use the Sebo G/X vacuum bags. HOWEVER, it has plenty of issues and is nowhere near the quality of a Sebo, yet they are very close in price when bought at a vac shop! Even with the Sebo's S Class filtration system they use not being quite as good as a vacuum with HEPA Filtration, I would still take it over the Sanitaire Eon. For most people, the S Class filtration would be acceptable UNLESS you're a severe allergy sufferer. And you're buying a German made machine made by a manufacturer of commercial machines that is a QUALITY BUILT MACHINE MADE TO LAST AND TAKE ABUSE! For that reason alone, it's worth the money they ask for a Sebo. If you do prefer the full size traditional style upright, look at the Sebo G series or Sebo Mechanical 300 - those models use the height adjustment dial over the fancy automatic computer controlled height adjustment the X series models use, they clean carpets better than the X series models, and it's one less thing to break down.
The Electrolux style upright that Blackheart suggested above is also a good machine. They do clean carpets well, and because the design has been around so long, consumable costs are very reasonable for it. However, because the powerhead is so wide, and the suction is only "average" for this machine, it would do only a fair job of cleaning bare floors. You would want to add a stick or canister vacuum to do bare floor cleaning. Also, beware that Electrolux dropped this model with the onboard hose for a reason - the hose was prone to clogging prematurely in certain households and cleaning situations. And there is a safety switch inside the housing that is pressed by a tab on the wand - it eventually wears down and requires replacement after a few years. Plus the hose is definitely a bit on the short side - if you intend to do more than just using a wand and crevice tool for edging around baseboards, such as cleaning couches and dusting, you might get annoyed with it. Best to have a small canister vacuum to add to it for tools use.
Also, don't make the mistake of buying a used Electrolux upright unless it says Aerus on it! Not Electrolux! The reason for this is that the earlier models in the 80s and 90s, like Human's Discovery II he picked up recently, have suction motors that don't produce very much suction and airflow by today's standards. And for a practical matter, the age alone means the motor is due for replacement soon after you get it. Best to leave those to a collector. The models made with the Aerus name, after the company was bought out by Aerus Holdings, they got a updated motor that is more powerful, and you will be much happier with the suction and airflow it produces. You can also look at buying a ProTeam Electrolux style upright if you would prefer to buy used, those would produce the same suction and airflow as a Aerus upright would. So this would be a good choice to buy used if you could find one cheap in your local Facebook Marketplace, Craigslist, etc.
And whatever you do, DON'T get rid of your Bernina upright just yet. Definitely hold on to it for a while and try to source a replacement motor for it. They are pretty good models, and most definitely worth repairing. When you're looking for motors, also look at replacement motors for Panasonic uprights. Certain models did use a Ametek motor that is nearly identical in appearance and size to your Ametek motor in the Bernina. So put that in your search bar when looking online.
Finally, I want to leave you with this thought: Spend the money and buy a QUALITY VACUUM! You spent the money to buy a condo, right? You spent the money to furnish it nicely, right? Then why not spend the money and buy a quality vacuum that will clean your home, NOT put tons of dust back in the air, be easy to use, and last a long time? Remember, in this day and age, that saying "You get what you pay for!" is so very true! If you buy a cheap Bissell or Hoover at Walmart, don't expect it to last long and definitely expect it to have problems.
