Manley Stingray & magnepan MMG's

Been hearing so much about tubes I am intersted in changing my secondary 2 channel system in my bedroom with a manley intergtrated stingray. I am currently using a mcintosh 7150, ( 150 WPC ) in a realativley bright room. Room size is 20 x 24, and ceilings are 13 feet. My concern is weather the 40 WPC would be enough to make the maggies sing like they are suppose to. Nothing wrong with the mac, but I love to try new things. Any input would be appreciated, Thanks....John..I will also be using a classe CDP-3 CD player.