The speakers used would influence the choice of amplification due mainly to efficiency and impedance. Low impedance speakers often are a very difficult load for receivers to drive (receivers are generally designed to handle 8 ohm loads, and anything less may be difficult for them to effectively support). Likewise, low efficiency speakers will benefit more from additional power than higher effeciency speakers. Forum regular soundhound runs a system that uses extremely efficient horn speakers (somewhere around 110dB or better, I believe), and he uses tube amps with ratings in the neighborhood of 5 or 10 watts - with power to spare. On the flip side, new forum regular wingnut7442 uses Polks, and she exchanged an Outlaw 7100 (100W/channel at 8 ohms and 165W/channel at 4 ohms) for a 770 (200W/channel at 8 ohms and 300W/channel at 4 ohms) because her speakers (4 ohms nominal and 88dB efficient) sounded better with the extra power. If you had a high efficiency 8 ohm horn speaker (such as something from Klipsch), I would suggest that adding a 200W amp would be unnecessary.