The Key Club hit all the right notes last weekend, with the smashing opening of Friday's Club Rubber (which left lines lingering around the block all night) and Saturday's benefit show by the Artist, who performed at the West Hollywood nightclub for more than three hours, jamming with legendary bassist Larry Graham (Sly and the Family Stone) and Fishbone's Angelo Moore. Among those who didn't miss the "Nothing Compares to You" encore were No Doubt's Gwen Stefani and Bush beaux Gavin Rossdale, Perry Farrell, watching the show from the sound board, Halle Berry, Tony Curtis and Urkel ("Family Matters' " Jaleel White). After the show, the Artist hung out in the VIP lounge, rechristened Plush, allowing admirers to join him at his booth two at a time. . . .