RGB LED strips ,60/ M and atx power supply

I posted previously about driving LED strips (5050 60 led/ M) from an Arduino through RGB amplifiers vs building a board with MOSFETs (special thanks to Paul for his insights).

The amplifier I am using is the same as the one at this link http://www.amazon.com/Signal-Amplifier-Range-Extender-Strip/dp/B0050CO6QW/ref=sr_1_3?ie=UTF8&qid=1397093568&sr=8-3&keywords=led+rgb+amplifiers

My question now is centered on safely powering the strips. I purchased a 600W atx power supply that has 2 dedicated 12v rails, each supplying 24A (48A total) of power. I am looking to power 45M total of RGB strips. As I understand this each strip can draw a max of 1.2A per meter (6A per 5M strip).

I have purchased 9 of the above amplifiers and plan to wire between 5M-10M to each power supply. For the most part they will be synched to music so they won't all be totally on at the same time. I have read (and verified) that through PWM each strip seems to use about 1/2 to 1/3 of the highest amperage they could require.

Is there any safety concerns I should take into account when creating a setup like this? From my observations I appear to be under the required wattage and amperage, and, I have taken steps to power each RGB strip independently where I can.

Thank you all for any thoughts you might have.