Get some WD green 4tb drives, they are much faster than those stupid hitachi ones, especially when you put them in raid0. Also that PSU is way overpowered, the 900 series is very power efficient, you should be fine with this one
Why don't you ask redditors whether they would be willing to send you a dollar, to help you pay for a replacement 5V@2amps wall wart?
You're correct, I misread the link.
Those 1/8" jacks are heavily current-limited though meaning the supplied 5v from the connector probably won't be able to serve as VCC. This schematic is actually for the board Sparkfun sells. It's designed to run off a 9v battery but any voltage would work as long as you tweaked the value of R4 to achieve the right collector voltage.
If using this schematic, a regular old power supply might be worth considering.