It took the intervention of Professional Footballers Association (PFA) and Football Federation Australia (FFA) to end the impasse, with an agreement struck on Wednesday afternoon that has given a final green light to the on-off move.
Parma first tabled its offer - which triggered a release clause in Antonis' Sky Blues contract - two days after the club's A-League finals hopes were vanquished at the end of March.
But Sydney, which wanted him to remain for one more season but was prepared to let him trial at FC Utrecht, questioned the timing of the payments, insisting on a lump sum for it to sign off on the four-year deal.
A relieved Antonis, who is an integral part of Australia's FIFA U-20 World Cup team bound for Turkey this month, expressed his relief.
"It has been on my mind a bit but I'm just happy everything has been sorted out," , he told The World Game.
"I want to thank Sydney, the FFA and PFA and now I'm free to follow my dream and hopefully go on to play in Serie A, just like Mark Bresciano and Vince Grella did so brilliantly when they were together at Parma.
"If I can follow in their footsteps it would be special.
"I learned a lot at Sydney and have received great help and advice from Alessandro Del Piero, Lucas Neill, Jason Culina and Frank Farina and now I can't wait to get over to Italy in July and get to work.
"I am looking to take my game to another level in Italy."
The outcome was bittersweet for Sydney, with CEO Tony Pignata labelling Parma as "unprofessional", and insisting it will seek FIFA sanctions if the agreement is not adhered to.
Under the terms of the deal, Parma must pay Sydney $100,000 now with further instalments in October and February.
"We didn't want to let the situation affect the player any further," Pignata said.
"It's not what he needed going into the U-20 World Cup and we wish him well.
"He's going into one of the major leagues in the world and it's a big opportunity for him. We all want to see him go on and become a regular for the Socceroos.
"He will be welcome back at the club any time.
"He can now focus on the Young Socceroos and not have this hanging over him. The situation was becoming frustrating for him.
"We are disappointed in Parma though. We tried to contact them on numerous occasions and they never responded and they have been unprofessional in their dealings with us.
"If they don't stick to the payment plan we will certainly seek FIFA sanctions."
Father Peter Antonis, who manages his son, said: "The last few days have been difficult but an agreement has now been reached and Terry gets to fulfil his dream.
"It was all weighing on him a little but you get ups and down in football and it's how you deal with them that counts.
"Terry has always looked to Tim Cahill as an inspiration and his ability to deal with all sorts of challenging situations.
"He deserves this opportunity. He has worked his way through the system from Marconi, Westfield Sports High, NSW institute of sport, the AIS and the Joeys.
"He's earned his shirt for the national team and now just wants to concentrate on the U-20 World Cup and then think about Italy."
Antonis, 19, will go into camp with the Young Socceroos on Friday ahead of a friendly against New Zealand on Monday in Wollongong before departing on Tuesday for Turkey.
The Paul Okon-coached Young Socceroos play their opening group game against, Colombia on 22 June (23 June 1am AEST). Their second match of the tournament will be against El Salvador on 25 June (26 June 1am AEST) before they face host Turkey on 28 June (29 June 4am AEST).
All the Young Socceroos matches at FIFA U-20 World Cup Turkey 2013,
plus the semi-finals and final, will be LIVE on SBS TV and streamed
online on TWG.
"We think we can do well and if we needed any inspiration watching the Socceroos play so well in drawing 1-1 with Japan has given us it," added Antonis, who shrugged off the effects of a stomach virus to come off the
bench in last week's 2-2 draw with Germany U-20s in Cyprus.
"I think we have a good mix of local players and players based overseas and we're going to give it everything we have."