I've been getting disappointed trying to upgrade an old system.
I have a 10+ yr old Sony HCD-461 which to me has always sounded tremendous for both movies and music.
But I should note that I am mainly referring to musical performance for the rest of this question.
I recently moved this system to another room and hooked it up to a pair of Yamaha NS-AW350s. Again the stereo sounded tremendous if not better through these speakers. (only 2 instead of 5)
I then first tried upgrading to a Sony STR-DE897 hooked up to the 5.1 Sony speakers I used to use with the OLD system.
To me it sounded terrible. Nowhere near the quality of the old Sony.
So I just traded that for an HK AVR-335. This sounds leaps and bounds better than the DE897, and don't get me wrong it is very musical and clear.
But to my ear, it still is not as articulate, smooth, and definitely doesn't seem to hold at high volumes like the old Sony HCD-461 system.
I'm not familiar with the HCD-461 but I think in general older pro-logic receivers were designed to have decent stereo reproduction. The pro-logic processing and center and rear channel amplifiers (often of much lower quality) were more of an add-on. These days most AV receivers are designed with features and DD/DTS processing first and stereo reproduction second.
NAD receivers have a good reputation for musical reproduction, you may want to browse this forum for a few opinions on them. Cambridge Audio sounds nice as well in stereo. I've owned both NAD and CA receivers and they certainly sounded better in stereo than any other AV receiver I listened to.
I haven't listened to them personally, but I've read quite a few posts about how the new HK AVR435 and AVR635 models seem to be quite good for stereo as well as HT. If you're limited to exchanging the HK for another model, I'd give one of those a try.