I searched the Irish Family History Foundation's database. It contains 12,000,000 surviving rcds for abt 65% of Irish counties. Rcds B4 1840 are sparse, B4 1800 rare. I only search the 65% which are.
For James Armstrong B 1801 +/- 4 yrs, I found 4 B rcds: 1799 Westmeath, 1799 Meath, 1800 Cavan, & 1805 Westmeath.
For Phoebe Lindsay B ditto, I found 0 B rcds, anytime, anywhere.
For a James and Phoebe marriage 1826 +/- 4 yrs, I found 0 M rcds for Phoebe and 5 M rcds for James: 1824 Tipperary, 1825 Cavan, 1826 Roscommon, 1829 & 1830 Meath. There is NO MATCH. It is unusual, but not unheard of, to have one party to a marriage transcribed, but not the other.
For a John and Catherine marriage 1826 +/- 4 yrs, I found no matching rcds for yr and county.
Google the Foundation's name to lead you to the database. Register, opt to be notified as rcds are added and browse. Pls post your search results to my genforum msg.