The Irishman saddles both Stone Age and Broome in the 12-furlong Vase, a race he won twice with Highland Reel in 2015 and 2017, while relying on Order Of Australia in the 10-furlong Cup.
The Ballydoyle handler also won the Vase in 2020 with Mogul and appears to hold a strong hand again in the Group One contest.
Stone Age, a son of the late super-sire Galileo, was considered one of the yard's top hopes for the Derby, but things did not pan out at Epsom and he could finish only sixth behind Desert Crown.
Yet he was a creditable third in the 10-furlong Belmont Derby Invitational Stakes at Belmont just a month later and showed his toughness when finding only Godolphin's Rebel's Romance too good in last month's Breeders' Cup Turf at Keeneland.
"We were delighted with him in the Breeders' Cup, he ran a very good race and had progressed from his previous run at Ascot," O'Brien said. "We've been happy with everything we've seen from him since then.
"It had been on my mind to go to Hong Kong since after the Breeders' Cup, we thought the track, trip and ground should all suit him fine, we're all looking forward to it."
Stone Age is only three and the best could be yet to come according to O'Brien, who added: "We think and hope he will (stay in training), obviously we think he's progressing and he definitely could progress again from three to four."
Stable stalwart Broome is a much-travelled eight-time winner and arrives in Hong Kong for the first time. A son of Australia, he has been a little tardy from the gates at times this term and missed a beat when sixth in the same Breeders' Cup contest as Stone Age.
However, he recorded a valuable success in the Hardwicke at Royal Ascot and O'Brien feels bypassing the Japan Cup in favour of this latest examination may see him in a better light.
"We were very happy with his run in America, he was a bit slow away, got back a little bit and finished off very well," O'Brien said. "We had it in our heads that we might go to the Japan Cup, it just came maybe a week or two too early and that's why we waited.
"We were delighted to have the opportunity to come to Hong Kong with him. He's in good form and is a very good natured, very sound horse."
O'Brien will bid to land the Hong Kong Cup for the first time and steps Order Of Australia up to 10 furlongs, having run over shorter distances in his last 15 outings.
The five-year-old's biggest win came in the 2020 Breeders' Cup Mile and he followed that with sixth place behind Golden Sixty at this signature Sha Tin meeting.
Though he has won over a mile and a half, that success came in a minor event at the Curragh as a three-year-old.
"He's been running all the time over a mile, but we always thought stepping up over a mile and a quarter would improve him more," O'Brien said. "He's obviously by Australia and we're very happy with him, we'll see what happens on Sunday.
"He has won over seven furlongs twice as well, so we kept him at a mile after the Breeders' Cup win, but we'd think there's a pretty good chance that (10 furlongs) will be fine."
He added: "Obviously you need horses that don't mind travel, have experience and are still in good shape," he said.
"It's a fantastic meeting, we speak to a lot of people who will tell you it's a great day. We always like to be involved and are delighted to be invited, especially for very competitive, high-class racing."