Dario is awful, sorry, just sounds really cheesy. Maybe I'm thinking of the 90s DJ Dario G?! Milo is nice but I thought of the Tweenies too. Dexter also reminded me of the serial killer TV show, plus I think it's getting more popular (which may cancel out the TV show association).
Liam is solid and traditional but I find it odd when used with non-Irish surnames.
Thank you all - I may have a rethink! I'm totally put off the name after the DJ Dario G comment...cant shake that association now! DH still really keen on Isaac. I'm a fan of Liam, we are Scottish/Irish so fairly traditional.