I still think you should get a better heatsink for the CPU, but it's your choice.
With a NH-D14 (or the flat version of it if you want to be sure it fits) would let you reach atleast 4.5GHz on that CPU with good temps. If you'll get a good chip you'll be able to go above 5GHz.
Although I understand if you don't really care about a high CPU OC since you only have 1 GPU so it barely bottlenecks it anyway.