Have a one story 1300sf townhome and I am looking into upgrading the filter media. Right now I am using a 1 inch merv 8 filter that I change every month ( Im afraid of going any higher and damaging the system). In the past year and a half I took out the cartpet, put in laminate flooring and had the furnace and ductwork cleaned but the wife is still having allergy/asthma issues. I . Now I am looking into a better filter system on a rather tight budget. I have no pets and the furnace is in the finished basement. With all the choices out there what do you recommend I look for?