After years of tossing back cosmos, Sex and the City fans are facing the end of the party, and The Sopranos may soon be sleeping with the fishes, leaving HBO devotees hungry for more edgy entertainment.

The network that created these bada-bing hits is already tinkering with new offerings, but as Carrie and friends end their fling with viewers and the Jersey mobsters whack their way to a finale, HBO execs face a unique challenge.

"Two of [HBO's] most popular programs may essentially be going off air within a year's time frame," Ted Johnson, national writer for TV Guide, said. "There will be a lot of pressure on them to come up with new hits. It's going to be a huge challenge."

Favorites like Six Feet Under and Curb Your Enthusiasm, which just won a Golden Globe for best TV comedy, are hitting their stride, so the network isn't losing its only hits, but replacing the two biggest programs won't be easy.

"Those were landmark shows and they've set the standard," said Karen Cooperman, a corporate communications manager and HBO fan.

While other networks drown in "reality" and ridiculously repetitive movie broadcasts — TNT recently aired The Perfect Storm three nights consecutively, during primetime — HBO has kept their shows innovative.

"Network programs are so processed at this point, you can just see the sausage machine the shows had to go through," Cooperman added. "HBO has more artistic integrity."

And even though the channel's programming is being shaken up — the popular prison drama Oz is also ending — viewers are confident that HBO will keep them glued to the tube by taking chances.

"They seem to go out on a limb and are fairly aggressive with the type of programming they offer," said George Lagusis, senior vice president of design for Fairmont Hotels and a loyal HBO viewer.

Steering clear of network fodder such as office sitcoms, cop shows and legal dramas, the HBO shows waiting in the wings tackle subjects not normally seen on the small screen.

Carnivale, a drama set to debut in the fall, is about a carnival traveling across the Oklahoma Dust Bowl in the 1930s. HBO Original Programming head Chris Albrecht called the show, which revolves around a radio evangelist and an 18-year-old fugitive, "dark and intriguing" in a recent statement.

"Everything I hear about the show is that it is very bizarre," Johnson said. "When that comes on, there will be a lot of attention paid to that show. It will probably be held to a higher level than The Sopranos ... just by the fact that HBO is held to a certain high standard now."

And good and evil are pitted against each other in a series set in the lawless town of Deadwood, which debuts in 2004. The tale begins in 1876 after Custer's Last Stand at Little Big Horn.

It may seem like a leap for the network to delve into historical genres, but the producers can turn dust to diamonds, Johnson said.

"The difference will be that David Milch from NYPD Blue is the creator behind Deadwood," he said. "It's going be a very intelligent Western that pushes the limits."

Another series slated for 2004 is a voyeuristic voyage into death-do-us-part commitment. Marriage will be shot solely in a New York City couple's bedroom, bathroom and closet, where secrets can't hide.

But with these shows yet untested, even diehard fans say HBO must maintain its edginess to stay in their good graces.

"If HBO doesn't come up with some more interesting shows — which they always seem to do — I'll go to alternatives," Lagusis said.

And while industry insiders generally have faith in HBO, the cyclical nature of success could play a critical role in the channel's future, Johnson said.

"The network that's hot often rests on its laurels," Johnson said. "The one that's down is desperate to find the next great thing and tends to take more risks, and then they're up again because they come up with a groundbreaking show.

"The question is: Is HBO so different that it won't be a victim to these kinds of fluctuations?"