Currently the highest core processor personal computer is the DS96. 96 nodes (effectively cores, hence the name), 192GB of RAM, 9.6TB HDD. However, because it came out in 2004 it's not exactly very powerful any more. Only 1.4GHz Efficeon processors. The newest mini supercomputer on the market is the Cray CX1. It's more powerful, but with fewer cores. Which, to be honest, is a good thing because the overhead for any program would be insane. But here's the max spec of it
2x Xeon quad core 3.0GHz
32 GB DDR2 800MHz RAM
320GB HDD
Windows HCP Server 2008 operating system
All that will set you back £16,368 which to be honest isn't too bad. But there's no GPU at all.