The Castletown men have progressed to the semi-final of the PARKER PEN SHIELD and will want to transfer their good cup form across to the domestic competition when they travel to Llandovery.
Caerphilly coach Mark Ring is under no illusion about how tough the job will be.
"It's a big one-off game. They are a good side who are right at the top of Division One.
'I expect them to be highly competitive and give us a tough match. It's the biggest game of the season for them, they have a partisan crowd who won't make it easy for us.
'But I'm looking forward to it, the players are on top of their game at the moment and we want to face these types of challenges."
Nantymoel are the only club remaining from Divisions 4-7 and boast an unbeaten run stretching 371 days. They face Bedwas.
Club secretary Gareth Thomas said: 'We are the only unbeaten senior club in Wales this season. Both Abercwmboi and Cefneithin are unbeaten in the league, but they lost in the Cup.
'It will be a big day for us, as only Maesteg from Division Two remain with us from outside the top two divisions. We have not yet thought beyond this round, but how nice it would be to have a home tie in round seven against a Premier club.
Llandovery, who act as a feeder club for Llanelli will be without centre Tal Selley, who will join the Scarlets for their Welsh Premiership game at Bridgend.
Maesteg play host to Pontypool in a game that sees an interesting match-up. While Byron Hayward has collected 329 points this season, his opponent may be Darren Morris, the former Youth cap, who is back after three years of injury.
Carmarthen Quins and Aberavon should provide a big match where goal-kicking could decide. Quins manager Anthony Dragone said: 'Being an ex-Wizard it would be nice to put one over one them.'
Glamorgan Wanderers will be looking to avenge a recent league defeat to Llanharan. Narberth recently beat Newbridge in the league, but with Newbridge on top of their game, expect a tight match.
In other matches Bonymaen host Beddau, and Cross Keys entertain Whitland.
Prinicipality Cup Round 6: Bedwas v Nantymoel; Bonymaen v Beddau; Carmarthen Quins v Aberavon; Cross Keys v Whitland; Glamorgan Wanderers v Llanharan; Llandovery v Caerphilly; Maesteg v Pontypool;Narberth v Newbridge.