Since you have all the peripherals, you could squeeze a i5-4690k (devil's canyon, best overclocking chip atm) and z97 mobo with a r9 280x (better) or nvidia gtx 960 (less good)
The GPU would be refurbished, with a $15 off code SPRING15
PCPartPicker part list / Price breakdown by merchant
| Type | Item | Price |
|---|---|---|
| CPU | Intel Core i5-4690K 3.5GHz Quad-Core Processor | $226.69 @ OutletPC |
| Motherboard | ASRock Z97 KILLER ATX LGA1150 Motherboard | $95.98 @ Newegg |
| Memory | G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory | $54.99 @ Newegg |
| Storage | Crucial MX100 128GB 2.5" Solid State Drive | $64.95 @ SuperBiiz |
| Storage | Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive | $47.99 @ NCIX US |
| Video Card | MSI Radeon R9 280X 3GB TWIN FROZR Video Card | $185.00 |
| Prices include shipping, taxes, rebates, and discounts | ||
| Total (before mail-in rebates) | $700.60 | |
| Mail-in rebates | -$25.00 | |
| Total | $675.60 | |
| Generated by PCPartPicker 2015-04-02 22:26 EDT-0400 |
Though the above build you would also need to add a CPU cooler if you want to overclock. Alternatively you could go for the dual core pentium g3258 and overclock the crap out of that, and get a better GPU.
PCPartPicker part list / Price breakdown by merchant
| Type | Item | Price |
|---|---|---|
| CPU | Intel Pentium G3258 3.2GHz Dual-Core Processor | $64.99 @ SuperBiiz |
| CPU Cooler | Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler | $29.75 @ OutletPC |
| Motherboard | ASRock Z97 KILLER ATX LGA1150 Motherboard | $95.98 @ Newegg |
| Memory | G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory | $54.99 @ Newegg |
| Storage | Crucial MX100 128GB 2.5" Solid State Drive | $64.95 @ SuperBiiz |
| Storage | Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive | $47.99 @ NCIX US |
| Video Card | MSI GeForce GTX 970 4GB Twin Frozr V Video Card | $319.99 @ Newegg |
| Prices include shipping, taxes, rebates, and discounts | ||
| Total (before mail-in rebates) | $713.64 | |
| Mail-in rebates | -$35.00 | |
| Total | $678.64 | |
| Generated by PCPartPicker 2015-04-02 22:28 EDT-0400 |
Probably the 1st one is a better bet... quad core really comes in handy with stuff like BF4.