120GB could be a bit of a squeeze, i like to go for atlest 240GB. then you have room to store a few things, say Photoshop so it loads fast... etc

i personally store a few games, OS, fair few programs and my documents (redirecting downloads, never know when your going to pull a few 10GB+ files afterall, thats a sizable chunk..) on my ssd and just give it a cleanup whenever it hits that 10% mark..