Should i upgrade my mobo and cpu

Looking for advice on upgrading my current system. I want to know what the best processor for my mother board is and will it be worth upgrading to this

Intel i5 3570k@4.5ghz, Arctic cooling freezer 13 cpu cooler. Asus p8z77-v lx mobo. 8gb Corsair vengance ddr3 1600mhz. Price £352



Current spec
Processor (CPU) AMD PHENOM II X4 955 SOCKET AM3 (3.20GHz/8MB CACHE) - BLACK EDITION

Motherboard ASUS® M4A785TD-V EVO: DUAL DDR3, S-ATA II, 2 x PCIe x16, 1 x PCIe x1, 3 x PCI

Memory (RAM) 12gb CORSAIR XMS3 DUAL-DDR3 1333MHz - LIFETIME WARRANTY!

Memory - 1st Hard Disk 128gb vertex 4

Memory - 2nd Hard Disk 500GB SERIAL ATA 3-Gb/s HARD DRIVE WITH 8MB CACHE (7,200rpm)

Processor Cooling SUPER QUIET 22dBA TRIPLE COPPER HEATPIPE CPU COOLER

Graphics card gigabyte 7970 ghz edition 1100/1500

Psu 750w.