If you head up to the Northwest part of Ireland, Carne, Enniscrone, Portsalon, Donegal (Murvuagh), and Rosses Point are all pretty darn good. Also up there is a little 9 holer called Criat Island(Spelling might be wrong). It is a really remote course, but has some excellent holes. Also if you spend a couple of days in Portrush there are a number of really good courses around there. Although we didn't play it the valley course at Royal Portrush got some high praise from a member we talked to. Castlerock and Portstewart are also excellent. Another course near Royal County Down that is quite good is Ardglass. Good luck with the planning!
Brendan