BISSEL, hepa filter, esp as got pets.
I don't know about one a month for cleaning filters though, ours NEED doing every week, takes about 1/2 hour, has 3 to do, rips up carpet if loose at all, and also the cylinder part lifts out as a seperate part to use on it's own if wished, to do car etc.
That's the best one we've had but was about £300.
tabetha