Don't rule out Co Meath. Laytown and Bettystown are both affordable and have good transport links to Dublin.
#Disclaimer - I don't know much about either of these towns, other than driving through them.
castlebellingham is only a village , ardee is a better option if you want a town with good motorway connections and all amenities close by , its half way between drogheda and dundalk , drogheda would be a better option but more expensive , louth tends to be a little cheaper for housing than meath , no good reason why it should be really , you are never far from a motorway in louth , its that small
, dunleer is another option but thats on the coast so more expensive i imagine ?
a blow in should never move to a town smaller than five thousand people in my opinion , the clannishness in small parishes is a sight to behold