I think Intel is not best buy SSD for now. Or 3350P cpu with your mobo.
If you do not want to OC then look Intel xeon 1230V2. or go with 3570k.
SSD good buy is Samsung PRO. Or if you look cheaper sandisk ultra plus is qawaome buy. Take 256GB
It is about same price as samsung pro 128GB. Bigger is better
But is 120GB is what u think is enough look cheap 120-128GB
PSU is enough. Best is look what psu is that to make sure. There is PSUs in market that do delivery only 450w and sticker says 750w.