Philadelphias estate specialists, Stephensons Auctioneers, will launch into spring with an April 17 Antiques & Decorative Arts Auction featuring 450-lots of quality items. Almost all of the goods including furniture, silver, artwork and jewelry came from private residences in prestigious neighborhoods. A professionally decorated home in Yardley (Bucks County), Pa. was the source for the trove of fine midcentury pieces that headlines the sale. The owners are moving to Florida and opted to consign their interior-design collection to Stephensons before relocating, said Cindy Stephenson, owner of Stephensons Auctioneers. Over a span of many year, culminating in 1984, the owners hired a Philadelphia design firm, TJ Ashjean Interiors, to decorate their home. They kept the receipts for many of the pieces, and those receipts will convey to the items