There is no example can be given.
Only explanation.

A Single rail PSU is much much stable compared to those two +12V Rails or more.

If you want to use a psu that has many +12v rails in it, yes you can, but make sure that the psu is confirmed stable, and has high amps on each of the +12V rails, such as the Enermax Galaxy DXX 850W and Enermax Galaxy DXX 1KW.

The two psu i've said above has at least 22Amps per +12V rails, and the Enermax Galaxy DXX 1KW as five +12 Rails in it.

However, single +12V rails psu is much much better, but still, those High wattage psu with single +12V rails is very very expensive.

Take PCP&C Turbocool 1KW as an example, the PCP&C is 1000W and utilize single +12V Rail with more than 90AMPs in that one and only +12V Rail.

It's the king of PSU.