> fast x86 cpu emulating
It'd be faster per Hz to emulate a PowerPC CPU via ARM, SPARC or MIPS CPU since with x86 you're having to cross endianness, and architecture so you're not only going to incur a performance hit, but power consumption and voltage requirements would likely be too high for an Amiga if it was x86. Heat is a consideration too. I'd personally vote MIPS since thats my favourite RISC architecture, but thats me.
Since there are some PowerPC chips being made ( Mostly SoCs ) it may be best to just get a cheap PowerPC with extended logic and libraries and plop that into an Amiga CPU slot. Using old Macs as donors, you could easily sell 68040/PowerPC cards for around the same price as the CSPPC goes, and I bet you they'd sell. I looked at 68060s, but according to Freescale's product page they ceased production and the last CPUs are EOL. Maybe someone has a Chinese supplier that can make them though. Making the boards in China may actually make it affordable.