I went from a Rotel integrated (RA1572, I think) to separates (see virtual system). The main reason was more control, particularly with phonostage. However, the comparison is not fair, as I replaced a 2K integrated with 15-20K in separates. Do they sound better than a 15-20K integrated? No idea. Accordingly, it is important to compare approaches on equal footing, while typically the change from integrated to separates also entails serious price jump.
Moving to separates
Does anyone have an experience they'd like to share about going from just an AVR or integrated to using external amp(s)? My Integra AVR has 100 W per channel (class AB), all channels driven, and sounds very good, so it is not clear to me that there is any advantage to connecting its preouts to a separate amp. Might be a total waste of money. Please mention your specific equipment. Thanks!