GTX 750 requires a minimum of 300W - see here. Your motherboard size is •Form factor: microATX - 24.4 cm (9.6 inches) x 24.4 cm (9.6 inches) so you will have to check out the computer case's size. see here.
Your upgraded Intel CPU isn't bad for a value CPU. see here.
Don't expect any miracles as it's a low spec PC for any gaming in my humble opinion but upgrading will help a bit.