Good stuff! How much time do you have?

Ruined but still wonderful, Clontygora
http://www.themodernantiquarian.com/site/1625/clontygora_court_tomb.html

Ballykeel Dolmen is a classic of the type
http://www.themodernantiquarian.com/site/1749/ballykeel.html

Just over the border is Proleek (your also about 40 mins from Newry to Newgrange, Knowth and Dowth, definitely worth half a day, go early!)
http://www.themodernantiquarian.com/site/1172/proleek.html

And ballymacdermot http://www.themodernantiquarian.com/site/1627/ballymacdermot.html

All three above are within 20 mins drive from Newry.

Further north you have Ballynoe stone circle:
http://www.themodernantiquarian.com/site/1048/ballynoe.html

Legananny Dolmen
http://www.themodernantiquarian.com/site/1055/legananny.html

Giants Ring near Belfast
http://www.themodernantiquarian.com/site/2243/giants_ring.html

which you could take in on a very winding route to Giant's Causeway, or you could go around the other side of Lough Neagh and visit some wonderful sites in Tyrone. There's a handful of excellent sites within a fairly small area:

http://www.themodernantiquarian.com/site/5369/creggandevesky.html
http://www.themodernantiquarian.com/site/2524/dun_ruadh.html
http://www.themodernantiquarian.com/site/2540/beaghmore.html
http://www.themodernantiquarian.com/site/5872/altdrumman.html
http://www.themodernantiquarian.com/site/6731/sess_kilgreen.html

and on the way from there to Giants Causeway you could take in this place: http://www.themodernantiquarian.com/site/2963/tircony.html and possibly here http://www.themodernantiquarian.com/site/3005/craigs_lower.html and http://www.themodernantiquarian.com/site/8383/craigs.html

There's plenty more to see, these are the ones I would take a day tripper to but if you have more than a day or two you could reach a more extensive list.

Today I finally had time to sit down and flick through the possibilities and almost had a little accident over the key board, that lot looks so awesome. Carvings, cairns, barrows, circles and a lovely henge. I love a nice perculiarity so I am particularly taken with The Giant's Ring.

Should be able to get to most if not all of those! Bounce! We are near Newry for 4daysish and probably up on the north coast for 3 daysish.

We are driving to Dublin on the final day so we are devoting that day to the Boyne valley. That's what I want to see the most...