If you are happy with the quote and the company installing the systems, then go for it. People on here are just giving you their professional opinion that the quote is cheap, they're not trying to poach the work. Me personally I'd go for a wired alarm if it can be cabled and by the sound of it, it can.
So to sum if you're happy with the quote, the equipment and the install company then give them the order to do the job. But make sure his price includes a warranty.