GTX970 is your first purchase, don't get any other graphics card, work out your budget after that then build around it, Intel i5's are decent priced, so a core i5 with a motherboard that it will slot into, check if the RAM from your current rig will fit, if not, 8Gb minimum, your hard drive from your current system will fit so you can continue to use that, so really if you cannibalise your current system you just need motherboard/cpu/possibly ram and the VGA, but nothing other than a GTX970.