From the various specs i found floating around, core is 256MHz, 1.15 - 1.2v.  I/O is 8 lines at 3.3v. I worked out the chip would consume around 1700mW. That'll be at the core voltage so 1.5A per chip should do it. Easily within USB power limits even with a typical DC-DC stage.

Unless we can find a micro that can output a 256MHz secondary oscillator, we need an external oscillator block (if the core - i/o is asynchronous) or a PLL to multiply the micro oscillator.

I'm not a fan of making a through-hole soldering kit. Way too geeky and more expensive than a fully built and tested SMT device.  While work with 250MHz, physical wiring tolerances are a concern. A large blob of solder in the wrong place may be OK at DC but at 250MHz, couples signals to other tracks. Happy to help with an SMT design.

I can't be of much help right now. On vacation with just a tablet!

Sam.