you probably want an A/V receiver instead of an amp like the Dayton APA150, especially if you plan to add a sub later.
You want something that can do bass management. plus you can use the optical output from the airport express to the receiver.
http://www.amazon.com/Yamaha-RX-V375-Channel-Theater-Receiver/dp/B00B981F38
You want something that can do bass management. plus you can use the optical output from the airport express to the receiver.
http://www.amazon.com/Yamaha-RX-V375-Channel-Theater-Receiver/dp/B00B981F38