Moheenly, From Kildare originally but now live in Dundalk, theres a Dunnes Stores not far from the Sainsburys in Newry. My advice would be to leave early, real early. Wife goes on a Friday morning before 11am & its just about bearable, on her return (about 12) the traffic is backed up on hill down to Newry & on dual carriageway its back to almost the Carrickdale turn off (about 5 miles or so). Saturdays are a nightmare & Sundays a complete disaster as opening is at 12.
Banbridge/Lisburn or Armagh might be worth considering. The extra driving time is offset by easier parking, less hassle in the aisles & fully stocked shelves.