Well I'm not so good with the stones in those regions (criminal I know!) but the Limerick area in the shannon region has some great castles. King Johns (which I live in sight of) is worth a visit - if a little touristy, and likewise with Bunratty. Both nice castles. Balina/Kilaloe and that Lough Derg area has some great stuff but bawn79 would be the man to talk to there. Obviously the Rock of Cashel is great too if you can get to there...and like churches.