The image has been posted in the right county too, but not the question
https://www.rootschat.com/forum/index.php?topic=211243.msg7521705#msg7521705 just the web link would have been fine.
Matchett is a common surname in the Tartaraghan / Montiaghs / Aghalee area. Tartaraghan parish records exist from 1825, but retained locally in the church, not online (St. Paul's church was consecrated 1819 replacing a former one of 1713). Montiaghs (Ardmore) was built 1785 but registers commence 1822 (offline).
http://rootsireland.ie/armagh/online-sources.phpAs common for Irish research the chances of "expanding my knowledge of the Matchetts into the early 1800s,
1700s and beyond if possible." is unlikely. Brownlow estate records eg rental books and some leases exist in PRONI but are extensive, time consuming and have to be consulted hands on. They will only list the head of house.
The Famine, as elsewhere, affected the area and many died or emigrated in the 1840's.
A search for deaths of the fathers post 1864 is possible in the civil records as is looking for marriages of siblings with the same father also in Lurgan District and a check of Griffiths Valuation 1864.