120 volts to 20 volts

I want to make a power supply that converts 120 volt (wall power) to around 12 to 25 volts DC and up to 20 amps. What would be the best way of approaching this? The first thing that comes to mind would be a transformer specifically designed for that rating, but those can be pricy and I don't know if I could make one. Are there other options? Would a reliable buck converter be hard to build? Any suggestions?
Thank you,
Ben

I buy prebuilt modules off of ebay. I'm currently using a 12V, 30A module. See Here.

Mike.

Switching supplies are definitely the most efficient, and these days can be quite cheap and readily-available. Be mindful that there may still be some high-frequency ripple on the output if not properly filtered though. Whether or not that is a concern would depend on your application.

DerStrom8 said:

Switching supplies are definitely the most efficient, and these days can be quite cheap and readily-available. Be mindful that there may still be some high-frequency ripple on the output if not properly filtered though. Whether or not that is a concern would depend on your application.

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I will probably invest in one of those modules then someday.
Actually my ZVS circuit just failed on me and I have had no luck so far fixing it, so right now power supply is no longer a major concern.