Armstrong popped in the 5-4 winner over home team Nottingham Panthers despite fatigue setting in - he's not in the best of shapes after being out injured for weeks.
The centre said he had loved skating over to the orange-clad Steelers fans to celebrate the overtime win over Nottingham Panthers.
His team had been 2-0 and 4-2 down to Panthers but Armstrong said the team had the composure and character to come back.
Armstrong said Cardiff Devils were a disciplined, difficult opponent - they play the league champions in tomorrow's Final - but said if Sheffield were at their best they can beat them.
The player and his coach both gave press interviews - but there was no sign of Corey Neilson, who had coached his last game for Panthers.