What Garcia said.
When looking at power as a criteria for an upgrade, figure that unless you at least double your current situation, it ain't worth it. Even then, doubling your power will only result in a 3 decible increase in percieved loudness. This might play outto a little (very little) more headrooom for a high power transient but, on the whole, ain't worth the effort.
For an apparant doubling of your current loudness you need about 10 times the power you now have,
Now, if there's a feature you simply can't live without then that's another story.
Me? The last time I felt the urge to upgrade was when DD/DYS came into play and obsoleted DPL overnight in the early 21st century. My last "upgrade" was a Denon 2802 in '03. It's got the meat I need (DD/DTS/DPL2) and I still don't feel the urgent need to upgrade. I'd rather watch that $$ grow in CD's.
If you really, really wanna change the sound of your system, look at new speakers or a killer sub.