Ohh yeah, i am sure
You can not just add all the rails. Since the dual rails actually get there power from one single rail. The dual rails are for ATX compliance.
If you allow lets say 25 amps through a cable, it runs the risk of getting too hot(the flow of electrons on a smaller cable generate more heat) and actually melting the wires protective skin(the black yellow orange green and red stuff that covers each wire). This would be bad. To prevent this they(Who ever makes the ATX rules) stated that NO cable should carry more then 20amps. Most PSU makers use 18amps with a 2 amp margin or error.
Even though my GameXtreme 700 has 4 x 18 amp rails they can only draw a total of 50amps accross all of them, not 72
Think of it
72 x 12 = 864 watts. too much for a 700 watt psu.
In the case of that PSU there is honestly no reason for rails as there is less then 18 amps of 12 volt power.
You can clearly see that the psu states it 12 volt output at 200 watts.
200/12=16.666666666666666666666666666667amps(Wattage divided by voltage = amperage). Not even enough to require rails.
Do you want to risk it when for 15$ more you can get something with a bit more power.
I want to make this clear, I DID run a X1900XT and E6600 system with a psu that has 18 amps, but it was more a proof of concept then anything(it ran fine during its time that way). That system now runs on a newer psu.
For more info on dual rails read the yellow box here(bottom of the pace)
http://www.silentpcreview.com/article260-page1.html