I disagree re newer builds being less well built - it really depends on the development, and a lot of the newer builds have much better BERs and even gas central heating which I would take over a poorly insulated, older block any day.
OP a lot of the newer blocks along the N11 seem very well built: Thornwood, Booterstown Wood, The Grange, Beechwood Court, Merrion Hall etc. I have known several people who have lived in them and there was never an issue with ordinary/everyday noise (can't speak for renovation work etc. but that kind of noise is not just an issue in apartments but houses too). Not sure if it is outside your area but might be a reasonable price point and the QBC bus corridor is handy for the nitelink and commute into town.