The 1080GLH should fit in the first slot, even with a NH-D14. I have it on the ASUS MAXIMNUS VIII HERO on the first slot, with the same cooler. The GPU is 2.5 slots, the only problem would be in your MOBO (ASUS P8P67 PRO REV 3.0) the heatsink on the MOBO chipset is quite tall, I hope it won't interfere with the GPU. The other thing I would be careful with is the PSU. Not sure if the TX-650W has enough power lines. The 650W are enough for the config, but you might need some cable splitters. I think it's a great upgrade for your system. The gain given by the GPU will be massive, your CPU will become bottleneck for 1080p gaming, but you will improve FPS many times over a GTX460.