I've been considering getting a Yamaha A-S500 amp, but I've also been checking out used older models such as the AX-497 (or RX-497), or even the RX-596. I realize the RX models are receivers vs. the AX amps. I don't care about having a receiver--can live with or without it. But I notice that the RX-596 has almost the same specs as the newer A-S500. Besides the extra connections (IPod dock connector, etc.) on the S500, is there any considerable advantage to this newer model? Have the internal components really changed much between these models (over a span of 10+ years)? If anyone has insight to offer on this, it would be very appreciated.

