room treatment on order...
Don't do anything more until these are in place. They change everything.
Lots of power is not important, quality is.
I'd suggest you listen for yourself, but include these three, very different sounding amps in your taste test:
- Pass
- Luxman
- Ayre
Your calculation seems off. Remember that power and volts don't use the same dB equation. Power is 10 log (Pnew/Pold) and Voltage is 20 log. Or I got them backwards. I'd check, but this site is free. :)
A middle of the road integrated with ~100 to 150 W will be just fine.
But seriously, get your room dialed in first. Better sounding rooms play better at low volume and sound like you have more bass. Choosing anything now will get thrown upside down after. :)
Best,
E