I'd really recommend getting a separate monitor, you could sell the iMac, and buy a second SSD and run this PC as a hackintosh (in a dual boot with Windows 8.1).
PCPartPicker part list / Price breakdown by merchant
| Type | Item | Price |
|---|---|---|
| CPU | Intel Core i5-4690K 3.5GHz Quad-Core Processor | £181.00 @ Amazon UK |
| CPU Cooler | Cooler Master Nepton 240M 76.0 CFM Liquid CPU Cooler | £79.99 @ Amazon UK |
| Motherboard | Gigabyte GA-Z87X-SLI ATX LGA1150 Motherboard | £74.15 @ Amazon UK |
| Memory | Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory | £52.98 @ Amazon UK |
| Storage | Crucial BX100 250GB 2.5" Solid State Drive | £73.95 @ Amazon UK |
| Storage | Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive | £43.50 @ Amazon UK |
| Video Card | EVGA GeForce GTX 980 4GB Superclocked ACX 2.0 Video Card (2-Way SLI) | £453.94 @ Amazon UK |
| Video Card | EVGA GeForce GTX 980 4GB Superclocked ACX 2.0 Video Card (2-Way SLI) | £453.94 @ Amazon UK |
| Power Supply | EVGA SuperNOVA NEX 750W 80+ Bronze Certified Semi-Modular ATX Power Supply | £64.90 @ Amazon UK |
| Monitor | AOC P2370SD 60Hz 23.0" Monitor | £111.99 @ Amazon UK |
| Prices include shipping, taxes, rebates, and discounts | ||
| Total | £1590.34 | |
| Generated by PCPartPicker 2015-03-06 23:18 GMT+0000 |