Risca of Three East scraped past Caernarfon 32-28 in the last round helped by a brace of tries from scrum half Rhys Morgan and they will find the trip to Ammanford just as tough.
The Two West side are top of their division and unbeaten at their Recreation Ground but only the cross bar saved them from defeat to Kidwelly in the last minute of round four as the final score finished 15-14 in Ammanford's favour.
SWALEC Three West's Gorseinon have been drawn at home to Tylorstown of Two East. Gorseinon defeated Penallta, another Two East side 21-16 to reach the quarters and will be confident of inflicting another blow on a higher division side. It needed a last minute penalty for Tylorstown to beat Skewen 22-20 in round four so a close encounter is on the cards at the Welfare Ground.
Tondu comfortably defeated Mountain Ash 15-0 to reach the quarters where they will entertain a Pontypool United side that provided the shock of the round after beating Aberystwyth of Two West 21-19.
SWALEC Plate quarter-final draw
(ties to take place weekend of 26 March)
Ammanford v Risca
Glynneath v Aberdare
Gorseinon v Tylorstown
Tondu v Pontypool United