A very good build with your budget.
120gb is too small for a windows C drive.
Many things default to C and when a ssd fills up, it will lose speed and endurance.
240gb should be minimum.
That will hold the os and a fair handful of games.
Yes, you can install a HDD later for extra storage.
But, see if you can't justify 500gb ssd up front and you may never need a HDD at all.
I like the Samsung EVO SSD better if the price premium is not great.
For a first time builder, I offer my basic build process:
MY build process:
Before anything, while waiting for your parts to be delivered, download
and read, cover to cover your case and motherboard manual.
Buy a #2 magnetic tip philips screwdriver.
1. I assemble the critical parts outside of...