Peni Pati won the New Zealand Aria in 2009.
Mrs La Grouw said another entrant, Lauren Michelle, was coming from America to compete for the title. She was one of five finalists in the BBC Cardiff Singer of the World competition this year.
"This year the prize package is valued at $20,000, it used to be worth $15,000, so I'm guessing that's the attraction."
Although the calibre of entries in the aria section had increased significantly, Mrs La Grouw said numbers in the open categories, to be held on Friday and Saturday, were down.
"Sadly we don't have the singing teachers in Rotorua anymore since Sherlie Dingwall died this year."
This year is the first year the Maori Song section is not being held, after only six people entered.
"It costs us $10,000 to run that class including the prize money and adjudicator's fees and with only six entrants it wasn't worth running it still."
She said it was a big shame to have to cancel that category as it was unique to Rotorua.
The contestants in the aria category will find out late on Saturday if they have made it through to the finals on Sunday night. All finalists get the opportunity to perform with the Auckland Philharmonic Orchestra at the finals show.
Mrs La Grouw said Sunday would also mark the final concert for MC Max Cryer, who had added his special comedic flair for the past 20 years.
Tickets for Sunday can be bought through Ticketmaster. They are $60 for adults and $45 for students and senior citizens.
New Zealand Aria First Prize Package:
* $5000 towards tuition or audition fees
* $5000 towards entry in the McDonalds Aria in Sydney
* $10,000 cash
Other prizes
* Second prize package valued at $10,000
* Third prize package valued at $5000
* All finalists receive $500
