usually the easy way to tell the bottleneck is if the gpu usage is low and the cpu usage is 100% or high then it's cpu limited and vice versa if the gpu is maxed and the cpu usage is low then your gpu limited.
the games make a big difference in where the bottle neck is usually and also because you've changed gpu architecture going from nvidia to amd/ati the frame rates may not have changed much/any because the games may be optimized for nvidia cards so you need a more powerful amd/ati card to get the same frame rates as a less powerful nvidia card.
to be honest i'm not sure just how much of a performance difference there is really in going from a gt 730 to a hd 7750 anyway, both are mid range cards, so the frame rate may just be about the same or an extra 2 or 3 fps anyway.
from your screen shots then yes i'd say your cpu limited, your dual core cpu is running at 100%.
Edited by terry1966, 11 May 2015 - 03:46 PM.