Cardiff currently prop up the Premier Division table but could use their cup run as a springboard to their season. "It's nice to have quietened a few people," said coach Howard Stone. "It was a potential banana skin coming down here."
Maesteg also narrowly avoided an upset in a nine-try thriller at Dunvant with a 24-39 win at the Broadacre. The Old Parish came close to throwing away a 17-point lead they rattled up inside 15 minutes as three second-half tries gave the hosts hope of a giant-killing before Roddy Boobyer's late try settled any nerves.
Elsewhere, 14-man Glamorgan Wanderers put in a plucky show before eventually going down 19-24 to Swansea in extra-time. The Wanderers had lock Jonathan Luff sent-off for stamping after 51 minutes but still managed to take the game into extra-time before All Whites skipper Gareth Newman grabbed the winning try to break the deadlock.
Newport edged a tense clash with Aberavon at the Athletic Ground, coming out on top 15-7 while Premiership leaders Neath blitzed Llangennech 51-7, the seven-try victory putting the All Blacks on course for a league and cup double.
Pontypridd were too strong for Cross Keys in their 5-44 win while Llanelli's conquerors Llandovery eased past UWIC, 43-11. And the quarter-final line-up was complete as Builth saw off North Wales's last representatives with a comfortable 28-15 win over Nant Conwy.