If you comfortable with a certain distributor, that might influcence your decision, though I recommend having at least 3 distributors. For central monitoring I am totally biased for Emgerency 24 since we have used them since 1981. Can't say enough good things about them. They aren't the cheapest, but they have a great response time. They are UL and FM listed too. 5 call centers around the USA.
Off the top of my head here is where you can buy the alarm panels from. Sorry if I forget anyone.
Bosch Security - Direct for the most part.
DMP - Direct only
Honeywell - ADI
DSC - Scansource, Alarmax, Tri-Ed, (lots of regional ones)
Napco - Alarmax, Tri-Ed, SES (lots of regional ones too)
UTC/GE (Interlogix-Caddix) - ADI, Anixter, CSC, Tri-Ed
There are some pros and cons to each alarm panel maunfactuer out on the market. For our larger commerical/govt. installs we have always been Bosch/Radionics. If you plan on doing bid work or think about doing larger jobs in the future, you really want to take a look at Bosch. Still our number one alarm brand but Honeywell has been catching up. They have a three year warranty on their parts unlike Honeywell. I'm not sure on the others, I think Napco and DMP is three years as well. Keep in mind like DMP, Bosch is dealer only and both of those companies have tightly controlled dealers bases. Last time I checked, DMP was looking for a 50k commitment a year. Both Bosch and DMP intergrate with the larger systems out there like Genetec, Miletone, etc. You can't keypad program the Bosch G series or their new B series panels. Their B Series panels is aimed at the light commerical/residential market but it took Bosch many years to catch up to others in the light commerical/residential market. I'm not sure either DMP or Bosch is a good fit for you
I would recommended Honeywell based on my experience to you for a couple of reasons One is there already a large amount of installed Honeywell systems by ADT. If you can get people to swich over, you can add more monitored accounts much faster. Great markerting resources, they do great job in that dept. Pre-made literature is still import in this part of the markerting. We have sold Honeywell panels since 2009 for the residential and light commerical market. I would say we have doubled our residential sales because Honeywell is priced pretty well. Honeywell has a huge range of panel kits with wireless motions and door contacts. Their 5800 wireless series has super reiiable. Other than your standard DOA parts, I haven't really had any bad 5800 wireless devices. If you want to go all wireless, the Lynx series panels have work out well for us. The wired/wireless panel for larger houses and small businesses, their Vista 21 IP panel has been a workhorse for us. I will warn you about their 6280 touchscreen keypads. Don't use them! Their older touchscreen keypads worked a lot better. Programming the Honeywell panels espcially the Lynx 5100 is a breeze. The downside of Honeywell is I can't say much about the others because I . Good luck out there.