"Is 500W overkill? It seems like such a good price...."
500W is very misleading. Current output is measured in ampere and not watt. Watt generally means nothing and is most of the time very misleading. Harmon/kardon receivers/amplifiers for example output a great amount of current and are among the strongest receivers/amplifiers in the business for example while Denon is among the weakest ones. The more serious reveiwers measure the current output and practically ignore the watt output when talking about power output.