The Sentria2 is supposed to be the best so far.
However TBH they all clean pretty much the same to me.
I currently use a Sentria2 (bought brand new), however I used to have a Ultimate G Diamond Edition (also bought brand new) and haven't noticed any real difference in terms of performance.
Even the older Heritage machines clean well if they're fitted with a new brush bar, belt and bag.
Please however note that Kirby machines are expensive to run.
Years ago I had a used Heritage machine and tried using aftermarket bags and belts in it... the belts didn't last long and the bags kept bursting. Performance was also poor.
A Kirby performs how a Kirby should preform when used with GENUINE Kirby parts.
The newer style HEPA bags from Kirby offer great filtration and superb airflow.
Personally I love my Kirby machine.
I've owned most makes of vacuum... most Dyson models and various SEBO machines ect ect and to me the Kirby is by far the best when it comes to deep cleaning carpets.
You have to get used to a different vacuuming routine though.
If you're going to clean each room individually constantly switching to the tools you will find it a chore and find it takes longer to clean the house...
What I do for example is vacuum the whole of upstairs with the machine in normal mode, then attach the hose (takes seconds) and then go around the upstairs rooms doing any jobs that require the hose such as cat hair on curtains and the edges of carpets. That's upstairs then fully vacuumed but while the hose is still on the machine I'll then do the stairs.
I then take the machine downstairs and do around all the edges and things in all rooms before taking the hose off again and going around all rooms in normal mode.
People say it is a major ball ache not having an on board hose, but if you forward plan your cleaning routine its just as easy as any other machine. As the example above I can vacuum our entire house from top to bottom and use the tools in every room yet I only switch the machine to tool mode the once.
The Kirby shampoo system is very good - I made a review of it on here not long ago - although again like everything else Kirby the shampoo is expensive. I paid £50 for a gallon container of it. The genuine Kirby shampoo works best.
While it is very expensive to buy a little goes a long way. I estimate the £50 gallon bottle would clean an entire standard 4 bedroom house, assuming every room is carpeted, at least 3 times.
To sum it up my Kirby Sentria2 is my only daily driver machine. It has replaced a DC39, DC41 and a Sebo X4. I have kept my Numatic George machine for the cars and messy jobs, but the Kirby has replaced it as a shampooing machine.
You'll find a Kirby a lot heavier than a Dyson and that genuine parts are a lot more expensive. You'll also find it feels rather OTT in terms of size at first... like trying to brush your teeth with a sweeping brush. However once you adjust you'll notice a MASSIVE difference in quality, workmanship and cleaning efficiency compared with anything else you've used.
And in terms of running costs, you do get what you pay for.
Personally I love my Kirby and wouldn't be without it
lol
