Power ratings are almost identical with the 4500 being advertising, from what I've read, having 1 watt more in quad mode.
I've been running mine in the bedroom for a few months and I love it. Mine has issues with the tuner dropping out every so often
then coming back on after a few mins. I'm not a fan of radio these days anyways.
The decoders every so often get loud static, I'm not sure if these units have the cold solder joint problems like the later big boys,
but I use the Involve QS board instead most of the time.
This is the loudest 22W I've ever heard in my life. With some big woofers, no need for a sub.
These early units are great if you can find them cheap and in good order.