Need advice on what to do for CPU and Motherboard

[Eko120]

So I bought my computer back in 2009. It is a Dell Studio XPS 435T. I have upgraded the graphics card, HDD and memory since I got it, but not the CPU and motherboard. I have no idea what do do when it comes to those 2 parts. My question is do I need to upgrade them and what should I get?

Budget - $200 - $300
Resolution -2560 x 1440
Games / Settings Desired - WOW - Ultra, Planetside - Highish, Rome Total War 2 - High
Any other intensive software or special things you do? - Adobe Suite for Designing
Country - US
Parts that can be reused - Graphics Card, RAM, Hard Drive
Do you need an OS? - No
Do you need peripherals? - No

Memory: 4 2GB DDR3 (don't know brand)
HDD: 7200rpm SATA (Fairly New)
PSU: Dell 475W Power Supply (OEM) soon to be EVGA 600w Bronze Certified
CPU: Intel Core i7 975 3.33GHz (OEM)
Mobo: OEM (cant find the model)
GPU: Nvidia GeForce GTX 760
Monitor: Asus 27"

[chazus]

EDIT: Just realized you have 4 sticks of ram.. need to check parts again.

You pretty much have two options.

i3-4330 setup
PCPartPicker part list
CPU: Intel Core i3-4330 3.5GHz Dual-Core Processor ($132.97 @ OutletPC)
Motherboard: Asus B85M-G Micro ATX LGA1150 Motherboard ($69.99 @ NCIX US)
Total: $202.96

or i5-4670K. It pushes your budget already, and I'd recommend a nicer board and maybe cooling.
PCPartPicker part list
CPU: Intel Core i5-4670K 3.4GHz Quad-Core Processor ($224.99 @ Amazon)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.98 @ OutletPC)
Motherboard: ASRock Z87 Pro3 ATX LGA1150 Motherboard ($94.99 @ Newegg)
Total: $349.96

I wouldn't bother recommending anything above, below, or in between this, to be honest.