> it could read from a spare USB2 hard drive that I have.
>
> I'm considering a Cobalt Qube 2.  They're available on EBay for
> between $200 and $300.
>

buy old (pentium-1 class, max 100Mhz) PC, unsolder ground wire from power
supply cooler and solder to 5V (so you get 7V power to cooler and it will
operate slowly and without any noise). remove cooler from CPU, will work
on radiator itself well, then put some 5400RPM IDE drive like seagate U5
that makes almost no noise.