The AMD CPU is not in the picture..... 3570k overclocks about 6% better on average than 4670k....however 4670k starts out w/ about a 10% lead so it never quite catches up.....but 4% to my mind isn't enough to sway ya choices.....
As for the processor.....there's a $10 premium on the 4670k on new egg. Amazon however has the 4670k for the exact same price as the 3579k - $220
http://www.amazon.com/dp/B00CO8TBOW
http://www.amazon.com/Intel-Core-i5-3570K-Quad-Core-Processor/dp/B007SZ0E1K/ref=sr_1_1?s=electronics&ie=UTF8&qid=1376847226&sr=1-1&keywords=3570k
There are a lot of great MoBo deals out there as vendors try and clear last generation socket 1155 stuff off the shelves. At the low end, these are very attractive .... at the high end, there's not much difference. And sometimes ya gotta look closer.....At 1srt glance there;s a $35 difference in cost between the MSI Z77 G45 and the the Z87 model..... but the Z87 comes with Killer Networking & Sound Blaster which accounts for a good part of the difference.
The other thing ya have to think about is what happens if ya MoBo dies 12-18 months from now, say for example while installing a new CPU cooler (had 2 1156 machines come back last month like this). With 1155 platform, there will be no 1155 boards available..... with 1150, ya spend ya $150 replace the MoBo and ya done. With 1155, ya spend ya $150 on the MoBo but ya 1155 CPU won't fit, so another $220 on the CPU.... and with new chipset, built in LAN, etc..... ya OEM version of Windows may not activate..... add $340 to the $150 expense.
So while I wouldn't recommend upgrading from SB or IB (1155) to HW (1150), I find no advantage to buying last generation MoBo / CPUs at this point in time.....yes the HW doesn't overclock as well .... but IB doesnt OC as well as SB either .... once OC'd, with HW's 10% or greater advantage (see link below) in performance, IB extra OC ability never quite allows it catch up ..... tho it does come real close.
http://www.anandtech.com/bench/product/701?vs=837