Good luck! I think you'll find that while it may be less expensive than buying a proven power supply, it may be more risky for your costly electronics to be connected to them, costing you more than you save.
If you know exactly what you're doing, no problem. If you're pretty sure you know what you're doing, it might be a problem.
Carnetix P1900's are for sale in the classified section for around $80. I'm going to guess that you'll spend half of that in parts and more in effort. But, this hobby is about doing it your way. If you come up with a solution, be sure to post it here. There will be plenty of people interested in it!