We've been with A & J Security for over 5 yrs now. Both in the old house, and now in our new house. Very professional company, and very competitive pricing.
We got the GSM (cellular) unit, so that we don't need a phone line. They were always prompt to respond, and contact us when our alarm would ring (fortunately all false due to family members going into our house without disabling the alarm).
Will be staying with them for a few more years, until given a reason to stop. May install surveillance cameras next.