I have the 600ESP which is the same thing less remote start. It's a good product as long as it's installed well. Nothing spectacular though, it just does everything as it's supposed to. You really can't go wrong with DEI but make sure the installation is good (that goes for any alarm.)

BTW, you cannot change the full trigger volume, only the chirps. If you want it to louder add another siren and/or make sure the one you have is facing the ground.