The Eagles picked up an impressive 42-12 win over Batley in the first round of the play-offs last week, while Halifax needed a late try to see off Keighley at The Shay.
Mark Aston’s men recently picked up a draw against champions Featherstone, and are in good form.
Gannon said: “We’re two wins away from the Grand Final so it’s all hands on deck.
“I’m looking forward to the game, it’s going to be tough because Sheffield are in good form and on form we’re probably the underdogs, but we know there are no prizes for second place.
“They’re a tough side and there’s no real chink in their armour, but we have home ground advantage and at this stage of the season that can mean a lot.
“We enjoy playing at The Shay and the fans are vital in these sort of games because when the chips are down, they can make the difference in getting you out of tough situations.”
Whoever wins Sunday’s match will take on Leigh next week for a place in the Championship Grand Final, which takes place at the Halliwell Jones Stadium on September 30th.