I have used Systec as a subcontractor. They have been ok, but definitely not the best IMO. They do things their way (product install), when they get good and ready. They would have to be the best deal going. There are lot of people that do security all over West Texas. Are you going to let them monitor your system or is it a stand alone system?
There are multiple companies in Midland, Lubbock and San Angelo. Not hard to find. Enertel from San Angelo is pretty accommodating. Not one of my pets, just one off the top of my head. Aprotex was another one we have worked with in the past.