Brighton started well and defender Tommy Elphick should have tested Scott Shearer early on when wastefully heading a Dean Cox corner over.
Bennett wasted a glorious opening for Brighton on the half-hour and Wycombe striker Matt Harrold shot inches wide after Scott Davies forced a fine save from keeper Michel Kuipers.
The hosts finally took the lead when skipper Andrew Crofts arrived late in the box in the 36th minute after Elliott Bennett set him up with a ball to the far post.
And former Wolves winger Bennett settled the replay on the hour mark by firing in low to the right Shearer from 30 yards.
Shearer prevented a heavier defeat for Gary Waddock's men by parrying a goal-bound shot from substitute Nicky Forster late on.