I agree with Tesla on this one. I have one computer PS with 4 lighter sockets fitted for powering my RC chargers. My newer one was $4 at MPJA. I snipped the connectors off and lugged the conductors onto 5 way binding posts mounted to a piece of folded lexan. I also mounted a toggle switch, mini DVM, 2 LEDs, and a boost mode power supply. This gives me a 5VSB low current supply and an LED that are on as long as the PS is plugged in. Flipping the toggle lights up the second LED and turns on 3.3, 5, and 12 volt high current positive supplies, and low current -5, and -12 volt negative supplies. Connecting the boost regulator to the 3.3 volt output, and the mini DVM, gave me a variable 4-30 volt output with display. It gives me just about any DC supply that I need. I'll admit that the dual binding posts cost much more than the core PS cost, but I wanted the convenience.
Your SCR supply will definitely need tons of filter capacitance, to be of any practical use. The ripple amplitude will be higher at lower average voltages. There are a couple clever circuits out there that put diode/SCR bridges in front of linear 3 terminal regulators. They phase control the SCRs to provide a voltage to the regulator, just above the input/output differential requirement. That way, the regulator power dissipation is minimized for a given current.