My thoughts are that for practical purposes there are a number of .22 rimfires that are lighter, handier, more accurate and powerful than most of the air rifles you're gonna find. I understand that you live in a suburban area, so may not be able to use a rimfire but the above factors are what keep me from sinking money into air rifles.
What is your reason for shooting fox in a suburban area? If a fox is becoming a nuisance it'll be much easier and cheaper to trap it.
