i decided to have a go at virtually building a pc to rival/copy the stock 2013 mac pro 6-core. i came up with the following:
intel xeon e5-1660v2 6 core 3.7ghz 15mb cache processor,
asus sabertooth x79 socket 2011 motherboard,
crucial 16gb ddr3 1866mhz ballistix tactical memory,
gainward gtx 770 phantom 4gb graphics card,
asus rog raidr express 240gb pcie ssd,
corsair ax760 power supply unit.
todays cost: £1838.98 (not including case, cpu cooler, dvdrw, wifi, bluetooth and thunderbolt).
you could swap the motherboard i've listed for an asus x79 deluxe which would give you dual gigabit ethernet connections, wifi, bluetooth and more usb 3.0 ports but this would cost a little extra. i could not find a suitable motherboard with thunderbolt connectivity at the moment.