I'm not having much luck with your query so far - I can see the marriage at St. Mary's Haddington road with the residences you mentioned, a check of directories around this time do not show either Murphy or Powells at either of these, so likely sort term or rental. Based on Patrick snr's occupation of farmer it would seem that this Murphy family would have lived outside the city somewhere, the problem of course is that there are a great many farmers with the surname Murphy all over Ireland, so establishing the right link could be difficult..
The bride's surname is a lot less common, a search for Edward or equivalent Edmond on the 1911 census only shows 12 results, two of these children and the other just 12 - none a Merchant. It's possible of course that this Edward changed his trade between 1911 and 1920... there are a number of Powell listed in Thom's Dublin 1921 directory, but no Edwards, maybe this Edward was employed by someone else or lived outside Dublin ?
One of the witnesses to the marriage is a Beatrice Powell, so may be related to the bride, a sister, cousin.. ?
Do you have any other details from family information that might help - e.g. siblings, possible places of birth for John or Anne, approximate year of birth, e.g. from death notice, headstone etc ?