Rotel RB870v RB 990 800 v 900 series??

Putting the power difference aside if one was to compare a Rotel RB 870 verses A Rotel RB 990 what might one notice. Is there a differnce in sound between the 800 series and the 900 series. I tend to think yes but did not have them head to head. I know the RTC 850 tuner preamp seems less grainy then the RTC 950 tuner preamp but what about the amps listed above? thanks