I would look for a G5 or newer. Kirby started installing the new Amodel fans starting with the G5. This new style of highly durable polycarbonite fan is almost indestructable. You can often find a good deal on a refurbushed G5 thru Sentria on ebay for under $300.00. OR you can buy used - as - is Kirby for much less, but then of course it's Buyer Beware!

As for filtration, the new Kirby cloth-like HEPA disposable bags are excellent at filtration down to 0.1Microns which is as good as any HEPA bags on the market for any other brand of vacuum. These bags will fit the G3 thru Sentria.

The Kirby is extremely easy to maintain. If you intend buy a used-as-is Kirby then you may need a new Brushroll, belt, and bag to get back to good as new performance. These items are eaisly replaceable by the user. If it was a heavily used machine, then the motor may require new brushes and/or front and rear bearings as well. These are also replaceable by the user if the user is mechanically inclined. If it were me, I would spend the extra money on a seller refurbished Kirby, then you don't have to worry about major repairs and the machine will also be shined up to brand new apperance. You can polish and shine your Kirby yourself with some Mother's aluminum polish, #0000 steel wool, and some clean rags. 

Hope this helps. We're here if you have more questions.

As far as I can see, only one of the links you provided includes the attachments which are worth close to $100. If you get a Walmart Kirby, it will include all the attachments and will have had a more thorough refurbishment. Everything will be new including the motor brushes and bearings. It will also have a limited warranty.

The G7d has the manual speed switch which was mostly a marketing gimmick and was discontinued the following model year. All Kirby's since the DS50 in 1965 have a 2 speed motor which automatically changes speeds depending if you are vacuuming with the floor nozzle (low speed) or using the hose with attachments (high speed). The manual speed switch actually gave you 4 speeds (2 speeds with floor nozzle and 2 with attachments) which proved to be too confusing to many users, therefore it was discontinued on the next model which was the G10d or Sentria.

Hope this helps you make a decision.

~Stan

I bought a seller refurbished Sentria with no warranty on ebay last year for $190.00 and I am extremely pleased with it so far. The machine was in excellent condition. The carpet shampoo system was also included in the sale. That Sentria is a beast, and my carpets have never been cleaner.

On a used machine, the outer bag should be fairly clean if the machine was used with a HEPA inner bag, however the outer bag can be removed from the mini emptor and washed on gentle cycle in your washer if you are not satisfied with it's cleanliness. Of course there are those horror stories of Kirby's being used with NO inner bag installed and of course the outer bag would be NASTY and should be replaced.

I think a professionally refurbished Sentria with warranty will cost upwards of $500 and should come with a brand new outer bag.