Hey. I am planning to buy the Wharfedale Diamond 9.5s. They have a power handling of 150 watts. Do I need the Yamaha Ax-396(2x60 Watt Min RMS) or the Yamaha Ax-496(2x85 Watt Min RMS) to take full advantage of the speakers? Also, since they have an 8" bass woofer i dont need a subwoofer right?