Placed in a two-goal ascendancy thanks to early goals from Manny Aguek and skipper Marco Jankovic, South cruised to the title in front of 4667, mostly home fans on Saturday, claiming both the trophy and $100,000 in prize money.
It capped off a remarkable turnaround for the club after the mid-season appointment of Sinisa Cohadzic, the Serbian-born coach guiding them from the relegation zone in NPL Victoria to champions of the newly introduced national second-tier competition.
"This is where South deserve to be; winning championships on the national stage," Cohadzic told AAP.
"We're always under pressure to win, that's our mentality and our DNA."
While Marconi will now look ahead to next year's NPL NSW season, South will begin preparations for the start of the new FIFA-backed OFC Pro League in January, where they will serve as one of eight startup clubs.
After starting brightly, the Victorians were gifted the game's opening goal when a horror backpass from Marconi midfielder Franco Maya allowed Aguek to steal in, sprint beyond defender Anton Mlinaric and laser an effort into the net.
Marconi laid some crunching challenges as they looked to spark a revival, but found their deficit doubled ten minutes later when Jankovic rose to meet a Max Mikkola corner and head home.
South would create more changes in the exchanges that followed but couldn't convert, wastefulness they were almost made to rue in first-half added time when Damian Tsekenis headed over the bar before keeper Javi Lopez was adjudged to have just prevented a header from Lachlan Griffiths from rolling across the goal line.
But with their two-goal buffer maintained, South were able to manage the game against an increasingly rancorous Marconi throughout the second 45 minutes and seal the win.
One of eight foundation sides in the new competition – that were joined by eight qualifiers sourced from the premiers from their respective states – South secured an unbeaten campaign with their win. Their only blemish across a six-game group stage and finals, a draw with Queenslanders Moreton City Excelsior.
"We're happy with how (the Championship) has gone," Football Australia board director Joseph Carrozzi told AAP.
"We're going to back this in for a long time to come and grow it."
