Hi Debh,
I have not been researching the Sunderland name other than trying to establish when the Rowsom family first came to Wexford. There is no mention of any Rowsom/Rowsome or Rowson as titulado (it was quite a lot of land - 335 acres ?) in Pender's Edition of Sir William Petty's "Census" of 1659 in Scarawalsh or Gorey Baronies, so my guess is sometime after this and before 1698. It might be worth checking Pender's Census for your Sunderland ancestors.
Other than that, you will find a few Sunderlands buried at Donoughmore Old Graveyard - see Dr. Jane Lyons excellent web-site at
http://www.from-ireland.net/wex/graves.htmBrief details of 70 baptism and 36 marriage records on the Irish Genealogy search engine - see
http://www.irishgenealogy.ie/csi/csi_main.cfmDetails of 74 Sunderland records or suspected records on IGI - see
http://www.familysearch.org/Eng/Search/frameset_search.asp It might be worth checking the British Vital Records Index Vol 2 as well, as this includes records not on the above link and I found one of my Rowsom ancestors this way.
And 18 Sunderland records on Griffiths Valuation for Wexford - see the searchable link on
http://www.failteromhat.com/I had a quick look myself, but could not find the marriage you mentioned (you should check for yourself, in case I missed it). If you know the parish concerned and if the C of I registers still exist, you may be able to inspect these manually yourself at the RCB Library in Dublin or commission a search. I also found some missing/unreported Rowsom records this way.
Happy hunting and good luck
skill