enough watts to drive these speakers? Help?

Greetings all,

I've got a friend with 89db efficent speakers playing in a 12'x15'x8' bedroom. He's looking at getting a 8 or 10 watt, low powered SET amp and is concerned if his speakers will play "loud enough".
He usually listens to classical and jazz at "moderate" levels at the loudest.

I compute that he should be getting 95db using only 4watts and the room should give a little more, perhaps 2db.

Are my calculations correct?

Anyone else that has a similar setup and can comment if it's loud and dynamic enough?

Thanks and happy listening!