If I saw this I'd say 'arry-a' not 'ah-ree-a'. I did some Googling. It appears to be a name used in Roman times and has roots in Latin and Armenian. If it's pronounced the way I think it is, I might prefer it to Aria.
1. I'm definitely right about the first 'a'. It would only make the long 'ah' sound if it had an accent mark over the top. In this instance the flat, short 'a' is correct.
2. Double letters should be pronounced separately. An Italian speaker would find this easy but I'm not sure how to make my English tongue do it.
3. 'ia' is not a dipthong so both letters are pronounced by themselves. Therefore 'ee-a' is the most logical ending as saying 'ih-a' sounds daft and you'd need an accent mark over the 'i' for 'eye-a'.
The pronunciation in Latin is: 'A-R/REE-A' (a like cat). Basically, I'm saying the first and last parts separately but right next to each other.
http://www.forvo.com/word/serra/#it < Listen to Heracleum saying 'serra' (greenhouse) in Italian. That's what I mean by the double 'r' being split in half. He seems to roll it too which is always funtimes. ;)
Aria is my favourite, Arria isn't awful though. Arya is a completely different name to me.
Aria is pronounced "Ah-ree-ah", with three syllables, and is an Italian word name.
Arya is pronounced "Are-yuh", with two syllables and is an invented name.
Aria Charlotte Rose was a combo I had on my own list for a while, perhaps you'd like it.
Arria will get misspelled constantly.