I have always liked Denon and Marantz. Marantz has a compact amp although limited connections on it (NR1510 is 5.2 and Cinema 70s is 7.2). If the Denon was working and is programmed into a control system, putting in another Denon would be the easiest as there would be very little programming required (if any) the X1700 would be a close comparison to the AVR-991 or if you are wanting/needing the latest and greatest the X2800 would be your next option.