With each of the hopefuls tackling two songs in the quarter-finals, they had to first perform an Abba song and James opted for SOS.
True to style, he managed to inject some angst into his version as he took to the stage in black leather and armed with his trusty guitar.
"You James Arthur-ed it all the way," Tulisa declared afterwards, before going on to predict that the singer would sell more records than anyone else - whether he won the show or not.
"Amazing to see you in the bottom two last week and I'm so disappointed for you," Gary Barlow added. "But it will not be happening this week, I'm sure."
With a Motown track still required, James returned to deliver Marvin's Gaye's Let's Get It On - minus the guitar and all scrubbed up in a suit and tie.
"Only you could get away with singing that song," Tulisa smiled, resulting in much teasing from Louis Walsh about his fellow judge being spoken for already.
James's mentor Nicole also loved the performance and predicted a baby boom as a result!
I do not want to see James Arthur again in the bottom two - he doesn't deserve it.
Meanwhile, Rylan Clark was loving the week's theme - opening the show with his take on Abba's Mamma Mia and following it up with a Supremes medley.
"I'm never going to buy the record," Gary said, in a bid to bury the hatchet with his nemesis.
"But it's week eight, you're still here - I have to respect you for that, coming back every week and putting on this show."
The last remaining group, Union J, were out to impress with Abba's Winner Takes It All and The Jackson 5's I'll Be There.
The judges were impressed with the vocal performances, but - given last week's shock result - their mentor Louis was on a serious push for votes.
"I want them here next week - I want them in the semi-finals," he said.
"First we had JLS, then we had One Direction ... I think the next big boyband is on stage."
Jahmene Douglas opted for Abba's I Have A Dream and Smokey Robinson's Tracks Of My Tears as his two songs for the night.
His mentor Nicole backed the other judges in praising the shy supermarket worker, branding his first effort "the performance" of the night.
"It was like you were saying a prayer and you included all of us," she added.
After Christopher Maloney's first track - Abba's Fernando - it fell to him to close the show with his Motown track.
His up-beat rendition of Lionel Ritchie's Dancing On The Ceiling saw positive comments from the judges about his vocals and energy, but - apart from mentor Gary - they still didn't seem convinced.
"When you're singing, I don't always believe what you're singing," Tulisa said, again referring to Christopher's performance as "dated".
Gary hit back on his act's behalf, stating: "I'm started to feel slightly uncomfortable with the criticism you're getting ... You've done really well tonight.
"I don't think people appreciate how much you've come on during the competition."
Find out who ends up in the sing-off and who has to leave the X Factor in Sunday's results show on UTV at 8pm.