Dropping through several regulators will work but the overall power dissipation is exactly the same. You are still dropping the same voltage at the same current so the same number of Watts is being dissipated as heat. It will almost certainly be bigger and more expensive though.
The LM2575 and a whole host of similar devices is the way to go. They are a type 'switching' regulator rather than 'linear' regulator. Basically, instead of converting the excess power as heat, they rapidly switch it on and off. By rapidly I mean typically 20 thousand times per second. If you imagine that each of these cycles has an off period and an on period, by changing the ratio of on to off the AVERAGE power can be altered. Always off would give no output, always on would give the same out as went in. Following the switch stage there is a filter to even out ( = take the average) of the switched pulses so it looks like a steady DC voltage again.
They are very efficient because the switching element is always fully off or fully on. When off, the voltage is high but no current flows so the power dissipated is zero (V x I = W so anything times zero is zero) when on, the voltage is zero and the current is high so W is still zero. Of course they are not 100% efficient but they are far better than linear types.
Brian.