Hi Mark,
Good to hear from you.
I'd say the fact that your gg grandfather listed his parents being from Hacketstown Parish, Co. Wicklow would mean they are most likely the Rathbawn Hughes. The Hacketstown RC parish covers parts of Counties Carlow and Wicklow so luckily you can eliminate any Hughes from the Carlow side.
Given the dates it seems like the baptism of your Michael Hughes would have been too early for the Hacketstown parish records which started in the mid 1820s. I did a quick check on the rootsireland website for any baptism records for the Hacketstown RC parish with the parents' surnames Hughes + Gibbons but unfortunately there were none.
Just to let you know what the tenant records list for Rathbawn:
1827 - William Hughes aged 54, farmer with 10 acres, 2 roods and 3 perches. Living with his wife aged 44, 4 sons and 3 daughters. There are also several sub-tenants on the land, namely:
Michael Doyle, 31, Labourer + wife and 4 daughters
Patrick Hughes, 50, Weaver + wife, 2 sons and 1 daughter
Bridget Connors, 70
1839 - William Hughes aged 64, farmer, same land. No wife listed so she must have died in the intervening years, 4 sons and 2 daughters. No sub-tenants listed.
Also:
1827 - Edward and Fergus Gibbons living in Rathbawn. Fergus was 45, wife 43, 2 sons and 4 daughters. Also Catherine Gibbons, widow aged 38.
In 1839, Fergus is listed as being 54, wife 52, 3 sons and 6 daughters. Catherine is listed, again as a widow, and 40 years of age (the ages are not always accurate as you may have noticed she only aged 2 years in 12!)
Hope this helps in your research,
Shane