Welcome to the forum Alej.
Like Coytee said about the db gain, the watts have to double.
I sold, then took in trade, a Sansui G5700 to a Sansui G8700DB (80 watts to 160 watts). I Large jump in watts and price for a 3db gain.
The biggest difference that I've notices is the type of watts (Digital, SS, Tube) and the source (digital such as off of flash drive, CD, Vinyl). Upgrading my sources rather than louder has done the most for my listening enjoyment.