I like this from a site compairing the 2 chips [4670]
''In terms of overall gaming performance, the Intel Core i5-4670 3.4GHz is massively better than the Intel Core i5-3450 3.1GHz when it comes to running the latest games. This also means it will be less likely to bottleneck more powerful GPUs, allowing them to achieve more of their gaming performance potential.
then 2 paragraphs down the say
''Both CPUs exhibit very powerful performance, so it probably isn't worth upgrading from one to the other, as both are capable of running even the most demanding games at the highest settings (assuming they are accompanied by equivalently powerful GPUs). ''
so would it not be worth the upgrade if the 4670 is ''massively better than the Intel Core i5-3450 3.1GHz when it comes to running the latest games.'' ???
see with that you get that 980 stick it in and it will do as you expect with in reason or it don't
but the end result is the more powerful the cpu the better the results