If you want low voltage and high current, it's best to lower the voltage at the transformer.
It's not too difficult to re-wrap a transformer to give a low voltage and then make a simple unregulated
linear power supply using a full bridge rectifier, and a large capacitor to filter the voltage ripple to an acceptable factor (you will need to calculate the capacitor size, it will be large).
You can get a 200A diode bridge rectifier for about $20 or find one in a scrap plasma TV which will give about 70A. The rectifier will produce heat so you need one with a heatsink.
When wrapping the transformer bear in mind that the rectified DC output voltage will be 1.41x the unrectified AC voltage, minus the voltage drop across the diodes.
If you just need a high current voltage regulator you can
do it with a bunch of mosfets. This would work fine with an ATX PSU or with a car battery charger for example.
Working with electricity is dangerous so it's important to calculate and verify your design carefully before building it. In the case of an electrolytic cell, the important and difficult calculation will be for the current draw, and you will need to design the power supply to be capable of supplying a significantly higher current than the cell actually draws. The question is, how big do you
really want to go? Do you really need very high current?
I would suggest starting with a small cell, then build more small cells and run them seperately until you really need to build a larger one. Bigger setups usually suffer bigger problems. Also you don't want to run a cell which is too big for the amount of material you want to process, so using multiple small cells means you can be flexible. Don't forget that for a larger cell, you will have a larger amount of silver caught up in solution at any time, it's a bigger investment in the cell.
This video gives the calculations for solutions for a 4 litre cell.