Help me make sense of this.

I have quad 405-II amp which is 100 watts per channel.
When I hooked up Yamaha RX-V3300 home theatre receiver, in stereo mode, wow I loved the sound !

Yamaha is 130 watts per channel. Does anyone know how much power I am getting in stereo mode?

Is Yamaha big current amp?

Does that mean I like powerful amps?

I didn't think surround receivers did music as well as a dedicated 2 channel amp ( especially seperates ) - so, I was pleasantly surprised at how music sounded through Yamaha - or has Yamaha improved their surround receivers to sound good in music as well ( in stereo )?

I want to know the answer, so that I might look for a more powerful amp in the future.

This question got me all excited, and I am puzzled...
Some one please shed some light on this - and I will appreciate that a lot.

It will influence the direction my next system will take.

I didn't think surround receivers did music as well as a dedicated 2 channel amp ( especially seperates )

Well built receivers can sound just as good as separates at modest power levels up to 150 watts - after all they are built of similar parts - you lose some flexibility though. Massive power supplies and huge heat sinks require lots of space - so monster amps tend to be separates.
The difference between 100 and 130 watts (measured the same
way) in a real world listening environment is virtually inaudible. I doubt it is a power or current difference you are hearing. I suspect you prefer the presentation of the receiver over the Quad.
I am suspecting Yamaha concentrates 6 ch powers to 2, thus putting out more than 130watts per ch. Am I wrong?
I doubt that power for all six channels is concentrated in two channels for stereo only. The specifications will tell you.
Your Quad is going on thirty years old. In it's day, it was a very good amp. Nowdays, it will have a hard time sounding as "musical" in comparison a lot of "mid-fi" gear. No doubt- you are hearing a lot of definition that you've been missing. There are a bunch of people that refuse to admit(or face the fact) that there have been a number of improvements with regard to the electronic components(passive and active)used in the manufacture of audio gear since the 80's. Count yourself blessed that you can hear the differences.
The Yamaha may have a slight gain in only 2 channel. The big difference is dynamic headroom. It will have tons more power for bass and peaks.
Although you don't say what speakers you are using it sounds like they are a better match for your yamaha. The quad is current limiting from what I read. TG
Thank you so much for the voice of experience !
I will try to hear newer units now...