Possible Clues:

• "Always Comfortable" mattress maker
• Mattress supplier for Hiltons
• Mattress brand that anagrams to "a rest"
• Mattress company with sheep mascots
• Firm once known as Sleeper, Inc
• Purple rival
• Retirement option
• Commercial prefix with -pedic since the 1950s
• “A champion of comfort for all,” according to its website
• Company whose mascots are sheep with numbers painted on them