Hi Adam B..........The NX6 will be able to utilize the x10 light modules once you add the NX540.
You can use the NX416 receiver and be able to use up to 16 wireless devices.
The pet immune motion , part # NX481 is available.
Keyswitch arm and disarm is a zone type that would allow you to use an old style keyswitch to arm and disarm the system.....perfect for upgrading from an older style system that uses a keyswitch.
The NX6 is good as long as you don't exceed the total zones available.....you have 6 hardwired zones available and 16 wireless....also be sure to get the keypad that will show you all your zones ...for example, you would not want to buy the 8 zone NX1308 if you going to have 24 zones.
Please feel free to contact the store for assistance as well.