The Western Province is in pole position, having beaten the North West Dragons by four runs in Cape Town.
Jonathan Bird and Kyle Verreynne both scored 42 to take the home side to 188-7 after being put in to bat first at Newlands.
Recently-capped Proteas Test all-rounder Ruan de Swardt was the pick of the bowlers, taking 3-23.
Rubin Hermann's 90 off 54 balls (including nine fours and four sixes) had put the Dragons on the path to victory.
Raynard van Tonder (34) and Wihan Lubbe (20) put the visitors in a comfortable position at 167-3, needing just 21 runs from their last two overs, but Beuran Hendricks (2-28) took two quick wickets to leave them all out on 184-6.