For my new PC I'm currently looking at getting an Intel i7 4790 (non "k" version) and a GTX 970 as the main components for the system. It will also be running an SSD, HDD, Network card, and 32GB of RAM. I've highlighted the two main components of the system, because, as it stands, the combined TDP of both the CPU and GPU is 684W (Gigabyte on the GPU side). I understand that TDP doesn't necessarily relate to the actual wattage draw of the component, however a page reviewing several GPUs (including the 970, here) details the 970s TDP at only 145W, which would make the combined TDP of the two main components at 229W – so:
a) Why do manufacturers state the TDP so much higher than what reviews state?
b) I was looking at getting a 750W 80+ Gold Modular PSU from Corsair, but after looking into this further, I contemplated getting a 450W PSU instead. Would I get away with doing so?