I am in the process of upgrading my 15 year old 2 channel audio system. I do not like or listen to home theater at all. I am an avid music listener. I have just purchased new (excellent) speakers and a new denon cd/dvd player. My question is about my old 2 channel yamaha receiver. It is 70 watts per channel and is 15 years old. It still works great, but my question is should I upgrade? Have there been advances in the last 15 years that make an upgrade worth it? I am thinking about upgrading to the yamaha rx-797 2 channel 100 watt amp. Thoughts?