The result ended Munster hopes' of a third Heineken Cup crown before the semi-final stages for just the fourth time in 13 years, while Ulster march on to just a second semi and a first since their title-winning campaign of 1999.
Ulster now face fellow RaboDirect PRO12 outfit Edinburgh in the last four at the Aviva Stadium on April 28, with a Heineken Cup Final against either ASM Clermont Auvergne or Leinster the reward for the winner.
And while Brian McLaughlin's Belfast-based side have had to play third fiddle to both Leinster and Munster in terms of Heineken Cup success this century, McGahan is convinced this could be Ulster's year.
"There is absolutely no doubt they have the capabilities of being a Heineken Cup-winning side," said McGahan.
"They made the quarter-finals last year and have progressed again to make the semi-finals.
"They have a tough nut to crack in Edinburgh but, if you look at their form over the whole season, they have all the capabilities of winning it.
"I thought Ulster were terrific (on Sunday), right across the park. They got into a substantial lead with three penalty kicks from over halfway… they controlled the scoreboard and they controlled field position, particularly in the first half.
"They certainly came to play, which we knew they would. Their defence was superb, the way they scrambled. It was a complete package."