Do I need to upgrade or just rebuild?

[tgvaughan58]

I feel like my CPU is starting to lag behind and feel like I either
A. Need to upgrade so key parts, or
B. perform a complete rebuild.
Specs:
CPU- Intel I-3 2120(sandy bridge) 3.3ghz
Motherboard- AS rock H61m-HVS(seems to be smaller than the average board)
Memory- 8gb (not sure on brand)
Graphics card- AMD Radeon HD 6670
Power supply- 400watts

Ultimately I would have $800 to spend on a new build/ new parts. I would not need a monitor, mouse, case, dvd drive, or operating system (dreamspark). I am looking for a build for World of Warcraft and want it to perform at max settings. What would be the best route to go given my situation?(In the USA)

[Deleted]

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-4670K 3.4GHz Quad-Core Processor ($219.99 @ Amazon)
Motherboard: ASRock Z87 Extreme4 ATX LGA1150 Motherboard ($119.99 @ Microcenter)
Memory: Crucial Ballistix Sport 8GB (2 x 4GB) DDR3-1600 Memory ($74.99 @ Microcenter)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($59.98 @ OutletPC)
Video Card: EVGA GeForce GTX 750 Ti 2GB Video Card ($159.99 @ Newegg)
Case: Silverstone SST-RL01B-W-USB 3.0 (Black) ATX Mid Tower Case ($35.98 @ Newegg)
Power Supply: Rosewill Hive 550W 80+ Bronze Certified Semi-Modular ATX Power Supply ($49.99 @ Newegg)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($16.99 @ Newegg)
Total: $737.90
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-02-22 12:07 EST-0500)

Guaranteed under budget before MIR (mail-in rebates). If all the rebates come back, you can conceivably add in an SSD or a CPU cooler for overcloking room.