A seat assembly for a choke valve assembly includes a housing having an internal passage, in which the housing is formed from a non-superhard material. The seat assembly also includes a seat disposed within the internal passage of the housing. The seat is configured to engage a needle of the choke valve assembly while the choke valve assembly is in a closed state, and the seat is formed from a first superhard material. In addition, the seat assembly includes an annular insert disposed within the internal passage of the housing downstream from the seat. The annular insert is formed from a second superhard material, and a maximum cross-sectional area of the seat along a longitudinal axis of the seat assembly is greater than a maximum cross-sectional area of the annular insert along the longitudinal axis.