SO you think “Big Brother” and “Survivor” are filled with back-stabbing opportunists?

Try a house full of aspiring actors playing a reality-TV game where, instead competing for prize money, the winner gets the lead role on an upcoming soap.

Say hello to Spanish-language television’s hottest new program, “Protagonistas de Novela,” the show that brings to life every actors’ worst auditioning nightmares and puts them on live TV.

“It’s the first reality show ever on Spanish-language TV,” said Telemundo executive vice president of programming Manuel Martinez. “The idea is to give Latino actors from all over, an opportunity to be our next stars.”

“Protagonistas” which airs five nights a week on Telemundo – the Spainish TV channel that’s merging with NBC – locked 12 wannabe TV stars in a Miami studio/house loaded with cameras and mics, a la “Big Brother.”

And like last summer’s edition of “Big Brother,” sex is encouraged.

“They’re banging away in there,” an avid “Protagonistas” fan chirped yesterday. Sexy scenes, do not make it onto the show because of FCC regulations, but viewers are left in no doubt about what they have missed.

The show became a hit so quickly the network had to put together a “hottest moments” clip show last Saturday night – after only one week – for viewers who wanted to catch up.

“It’s amazing I was just watching it because I saw some advertisments for it,” another fan says. “Then all of a sudden my friends started calling me about and my cousins and everybody I know is into it.

“We had a get-together the other day and I said please is there anything else we could talk about?” says the female fan.

The show is off to a strong start – with ratings that match those for early episodes of “Betty la Fea,” a show that went on to become one of the most popular Spanish-language soaps of all time.

Players spend their days taking singing, dancing and acting lessons. Each week two are nominated to be banished, one by the show’s judges – who base their decisions on the player’s performance skills – and the other by the housemates who have already begun trying to form alliances and cliques.

The final decision is made by viewers who cast their votes by calling a toll-free 800 number on Monday nights during the show.

Among the contestants the usual reality show roles of master manipulators and doe-eyed victims is already beginning to emerge.

Fabian Rosenthal, the 31-year-old Argentinean whose bio says he’s been in two independent films, is the first out of the gate as a scheming mind-jockey Richard Hatch type.