Hi OP,
Okay. I can see that you need a gaming computer. To be fortunate enough, you already own an awesome gaming processor with sufficient size of physical memory. For HEAVY gaming, you need 4 basic things.
> CPU (Checked)
> GPU
> RAM (Checked)
> PSU
For your rig, all you need to upgrade are GPU and PSU. Nothing else. There are LOADS OF GRAPHICS CARDS in this world. From cheaper to the most expensive one like GTX TITAN. As per your requirements, I suggest you to buy R9 270X. In the official records, it is noted as budget graphics card but trust me, I'm playing games like Spec Ops: The Line, Wolfenstein The New Order, Watch Dogs, Far Cry 3, Max Payne 3, Assassin's Creed IV: Black Flag, Syndicate, Metro LL Redux and Tomb Raider in ultra graphic settings. It's considered to be a bang for the buck i.e., an inexpensive card with high performance clubbed inside. This card can play ultra settings in FULL HD as well. If you aren't satisfied, you can rule beyond this level by affording R9 290/R9 290X/GTX 770/GTX 780 (or) even GTX Titan. It's your wish, OP but think of your budget when going through expensive dedicated video cards. These are just graphic engines and in here, the brands play a vital role. The best brands I can ever suggest you, are Sapphire > MSI > EVGA. Those brands provide full efficiency of the selected graphic engine.
Selecting your favorite card is easy. But the important part comes in choosing the PSU. You can choose whatever you need but I recommend you only 2 power supply units and they are as follows:
> Seasonic 620 W
> Seasonic 550 W
Reasons: Seasonic has bagged tier-1 PSU's i.e., they are made with good build quality with amazing ampere rating in +12V rail which is really necessary when your computer turns into a gaming machine. If not satisfied, you can choose Corsair. But when you buy Seasonic's 620 W PSU, it provides a big headroom which helps you to upgrade your PC components in future without bothering about power supply requirements. It's 620W supply will be fair enough.
Hope I've helped you, OP. Have a nice day.
Edit: And I forgot to comment about your motherboard upgrade. I think you need to reconsider it because the Z chipset boards are only for the CPUs which are meant for overclocking. The processor you've got is non-k version which means overclocking is not possible at all. Stay with the current motherboard if it comes with PCIE x16 slot. This expansion slot makes any graphics card to fit inside your PC. Otherwise, buy any affordable H87/H81/B85 Chipset board. Remember, motherboard does not play a role in enhancing the gaming performance. It is just a basement for adding the components.