Stoinis replaces West Indian Nicholas Pooran, while Ul-Haq comes in for Englishman Richard Gleeson.
Stoinis, the 34-year-old Perth native, is a veteran of 127 international matches across formats for Australia, and has a further 250 T20 matches worth of experience.
He also plays for IPL outfit the Lucknow Super Giants.
Durban’s Super Giants will play the Pretoria Capitals in Centurion on Thursday.
