UPDATE!!!!!!!
After all of your wonderful advice, I have great news! Shocking news!
Before contacting this forum, I had already been shopping around: I either looked at or considered the Hoover WindTunnel, Riccar, the Sanitaire (but worried about the cloth bag eventually not being conducive to my health), eliminated the Dyson and Oreck as they were outside of my budget and had never heard of or seen the Sebo in any of the shops I visited.
After so many Sebo Felix recommendations from your responses, I felt inclined to go to Craig's List. I entered the words: UPRIGHT VACUUM in search and only ONE single entry appeared in the entire Puget Sound area of Washington State: A brand new Sebo Felix for $250!
I called the seller, went to his house, VACUUMED around his house with the Sebo and purchased it with warranty, attachments and two boxes of bags. The seller has been selling the Rainbow Vacuums for 20-some years and took the new Sebo in trade - it's a long story.
This Sebo is the best vacuum for carpets I have had thus far, and I have had many. There is one negative: it is heavier than I would prefer, but I purchased it because of its ability to clean, its sturdiness, its lack of detectable exhaust, its ability to manuever so easily, vacuum close to the edges and fit easily under furniture. It "feels" and behaves like a very high-quality machine. For the price, I feel that I could not have done better.
Someday, when I have recovered my health, I will have my own house again and I will have wood floors so that I do not have to have my carpet cleaned every six months.
Thanks again to all who shared!