Tonmawr were given a taste of what life could be like in the Premier Division next season and they can be proud of their performance.
"Llanelli are a class side and they showed their cup credentials," said coach Jason Hyatt.
Carmarthen Quins had beaten Glamorgan Wanderers 9-6 in the league at the Memorial Ground this season but their 31-26 cup success in Cardiff was a surprise victory.
The only disappointment for Quins was the way they allowed the Wanderers to come back into the game after taking a 31-12 lead.
"We made problems for ourselves in leaking two tries in as many minutes but overall it was an excellent team performance," said Quins team manager Steffan Thomas.
"Our set piece play was was superior throughout and the scrum was also a key area in the victory."
Cardiff built up a big lead at the Bridge Field against Bedwas only to concede three tries to the home side before edging home 34-24. It was the Blue and Blacks second visit to Bedwas in a week after being beaten 21-17 in the Premier Division.
"We had Cardiff on the ropes after the break and were just seven points adrift but we only have ourselves to blame for not reaching our first SWALEC Cup semi-final," said Bedwas coach Steve Law.
Cardiff made many changes from the side that lost the league match to Bedwas and they raced into a 24-5 lead by the interval. When Cardiff flanker Jake Thomas was sin-binned with the score at 31-24 it looked odds-on for a Bedwas victory but Cardiff rallied to force a late penalty and seal victory.
Aberavon led Pontypridd 13-9 at the interval but with Ponty not having been beaten in a Welsh Cup match at Sardis Road since 2001, a second half rally was expected. It came with such force that Ponty ended up destroying the Wizards, 41-16.
The visitors were not helped by a series of misdemeanours which saw Aberavon forwards Darryl Thomas and Marc Breeze yellow-carded before Breeze was red-carded on the touch judge's advice. Paul Breeze then joined Thomas in the sin bin for dissent and Ponty took full advantage.
Ponty team manager Richard Langmead admitted his side had been poor in the opening period.
"We were terrible in the first half and a few home truths were said at the break, but we upped the tempo after that and kept our discipline."
Kenfig Hill stormed their way into the semi-finals with a surprise six try victory over Two East side Brynmawr.
The Mules were always too strong for their visitors and touchdowns by Lee Williams, Ray Evans, Rhodri Clark, Thomas Maund, Mark Fitzgerald and a penalty try kept the scoreboard ticking over at regular intervals.
Lougher already had a big Two West victory over Aberystwyth at home this season and they confirmed their superiority with a convincing 38-19 away success at Plascrug.
In the battle of the Two East sides at Cae Fardre, Llantwit Fardre edged out Rhydyfelin 23-17 with the kicking of Steve James proving crucial.
He converted both tries by Ben Lee and Geraint Lewis and added three penalties to boot his side into the semi-finals.
Maesteg had a tricky visit to Waunarlwydd to overcome having lost at Roseland Road earlier in the league season while only drawing their other league meeting at home. Typically, it was a close encounter before the Old Parish won through narrowly, 16-14.
Trebanos made the long trip north to Bethesda worthwhile but it needed a strong second half performance to put them into the semi-finals.
The Two North side had proved their equal in the opening period which ended with a 6-6 scoreline, but the Five South West outfit cut loose in the second half to roar into the semis with a 33-6 success.
Four East side Abercarn were made to work hard against Bridgend Sports before beating the Five South Central team 13-9.
Pontardawe of Four South West travelled to Risca of Four East and won 27-22 while in the other quarter-final, Senghenydd made home advantage count by beating Birchgrove 17-11.