You will still have a transformer but its just real small being it gets ran at high frequency instead of low frequency.
For what if costs to build and the specialized parts needed your money and time ahead to rework a 600 watt computer power supply to just put out its full wattage on the 12 volt circuit and then just bump up the output voltage a little.
Or strip down a pair of matching smaller units and build a parallel system. Use two computer supply's with 20+ amp ratings for the 12 volt outputs and tie them together with the output voltages raised a little.
With a Little clever tweaking the voltage reference feedback circuit of one can be tapped into to control two power supply's.