enough power?


Finally getting ready to install ELK M1G. I have decided to add the elk water shut-off valve, but am unsure if I need additional power.
I have added up the amp requirements of my current set-up (6 motions, 10 water sensors, 1 output and 1 input expander, 1 m1xsp for thermostats, 3 mics, listen-in board and phone board and a few relays.) In stand-by comes out to just under 500 milli-amps. I have a 1 amp siren and a 0.21 amp strobe in alarm.
Can I add the ELK valve (one amp, but only 5 secs when needed) without adding additional power supply??
Am I missing something? Thanks
The manual reads that you can run it from the M1 directly. I wouldn't. I have overcurrented the M1 on a number of installations. I am a firm believer that more power is better. I really like the ELK 4 amp power supply coupled with the PD9HC power distribution.