Use of a big filter with shedding animals, means the air will stink. My complaint against the thick filters, that only are changed once a year, it first, they add to the air restrictions and reduce efficiency of the system, but most important they collect smells. These smells stay in the filter. They are transmitted thru the house as long as the filter is installed. To combat this, room freshner pads are sold that are placed on the filter. IMO, the filter should be changed monthly or sometimes biweekly. If you have wood or tiled floors the filter needs to be changed more frequently. Shedding dogs, are probably the very worst condition possible for a filter to work in. If the return is close to the floor, I would have a filter inside of the return, and would check it weekly if I had allergies. You might have a Ecoquest demo in the home. This air cleaner is superiour to any filter sold today.

If you are wanting low maintenance, then stay away from electronic filters. They work well but require monthy maintenance to work properly, and are pricey. I would recommend the thicker media filters like the airbear brand or something similar. They are about 4 inches thick, pleated with lots of surface area which makes them ideal for someone that only wants to change the filter about every 3 months.
I don't know if I would pay for a duct cleaning, I probably would just open the vents throughout the house and run a shop-vac hose down them as far as they would go and call it good. I have heard of cases were people have had their ducts professionally cleaned and loosened things up and made things worse.......IMO

Get A Trane hp ,add the Clean Effects air cleaner and some uv lights.Duct cleaning is a money making scam.I have been behind the cleaning companies before.The duct ends up butchered and half cleaned.

Thanks for your opinions on the duct cleaning. I have doubts myself as to the benefit but DH is the one wanting this.

Bob--are you saying that using the regular pleated filters in the return air ducts is more effective than adding an air cleaner to the system? We use the white electrostatic kind now that are supposed to be changed every 90 days and we try to remember to change them every 60 days or so. All of the reading I have done seems to indicate that the media filters are the best type to have for allergy sufferers. To what degree would the efficiency be reduced over using the pleated filters?

Bama dude-thanks for the input. I know you are a big Trane fan from reading your posts and I have nothing bad to say about their systems. People I have talked to indicate that Rheem/Rudd is a bit more economical though and I have had past experiences with those brands that were very positive which is why I am inclined to go with one of them. We inherited the Goodman system when we bought this house and have had nothing but bad experiences with it. I've read that Goodman is getting better but I don't want to take my chances.