The warm, rich sound produced at any volume.

Minor... but the rear channel output is somewhat low... the Fosgate "wrap" design causes this.

I absolutely love this receiver! Harman Kardon consistently produces outstanding equipment. The sound quality is the best I have ever heard from any receiver under $1000. Put it this way... in one of the top stereo shops in the country, they were demonstrating $25,000 speakers using this receiver. The remote is kind of strange, but you get used to it. Try the "test" function... can definitely improve the output if the room is not symmetrical.