I decided on the Air Pura R600 due to its robust construction and simple controls. The idea of 18 lbs of activated charcoal was appealing since the grand kids mentioned that the house had a smell at times and I noticed kitchen odors occasionally myself. So far so good with the odor removal. It takes a while, but the R600 eventually clears the air. I'm hoping that my allergies are improved as well as they were particularly bad so far this year. Due to the open kitchen, nook and relatively large two story family room a purifier with the capacity of the R600 is required to adequately handle the load. I really like the completely variable fan speed so I can choose exactly the speed and noise I want to put up with. The family room always had a dust issue more than other rooms so I am hoping for improvements there but it's still too early to assess the results. The impression I have is that the Hepa and charcoal filter life "should" be decent but I'm a bit concerned about the prefilter. The description of the R600 indicates that it can simply be vacuumed from outside occasionally and replaced annually but, to me, that looks like a pain. I'm not sure how effective vacuuming over all those tiny intake holes is going to be. Based on the included "manual" - a very unfriendly and primitive pamphlet - you need to remove all three filters in order to change out the prefilter. That seems a little non-user friendly to me.
One of the reasons I liked the large amount of activated charcoal in the first place was that I had read you could buy replacement media and refill it for much less than the $199 replacement filter price. Unfortunately, I haven't yet been able to find any place that sells activated charcoal or anthracite media cheap enough to make refilling worthwhile so I may be stuck with the $199 charcoal filter replacement every couple years. We will see if I regret not having filter life indication or other bells and whistles, but so far, the R600 does meet my purchase criteria.
Shipping seemed to be a little too slow and it took over a week to get the notice of shipment so, if in a hurry, you might want to go with a different vendor. I used Allergy Buyers Club via the Amazon site.