Well building your own score a much higher badass factor overall, but you can get steals on ebay sometimes too.
I got 2 brand new meanwell sp-500-15s off of it. One for $60 and one for $75. There normally like 280-300 each but that gets me 64 amps at 15v for $135. As for the slot car idea i though about using a train transformer but was worried about how stable the power would be.
Word of warning though dont start two of them up at once they draw about 7-8 amps 120v inrush and can kill a breaker lol.