Seasonic is indeed very good quality and the X460/400 is indeed fanless.
A reputable PSU from companies such as Seasonic, XFX, Corsair, and Antec alongside a select few others is highly recommended.
Since i dont know what your budget is... I'll give you a few series of PSU's i'd like to recommend to people.
Seasonic Gold X Series , M12II series, S12II series
XFX Pro / Core Series
Corsair HX /TX V2 / TX M series
Antec units HCG/ EA/ TP series