I think the Seasonic X400 is a good choice, as it might allow different options in the future, even a mid end dedicated GPU etc. But if you feel you wont be using much more and want a silent PSU, you could try picoPSU and alikes, they have a lot of sub 200W PSU depending on your needs, for example Premium picoPSU-160-XT/16A 192W AC-DC
, this would also allow you for a smaller footprint case as they use an external brick, but it really depends on each needs, i been running mine more more than a year and im pretty happy with it, and under very light loads they consume less than higher watt PSU, but as i said been also pretty happy with my X400, both are good choices depending into what you aiming, as an alternative you can also look into. Another option, probably not as good as the seasonic, but seen decent comments is the FSP Group AURUM GOLD 400W
, much cheaper but i haven't tested personally to know first hand, i really wish FPS would give SPCR a sample to see how it stacks with X400.