hound dog: Yes, you could hook up an amplifier to your H/K reciver. It has pre-outs for every channel.
Better move? Better speakers? Your speakers are always going to define more of your listening experience than electronics -- you probably already know that. The (right) electronics, behind them help, but it's being able to reproduce the audio that defines "better" music sound.
So you may have good speakers but have just matched them, unfortunately, with the wrong electronics. For example, let's say that the speakers you mated it with are just a bad combo with that receiver... like my Klipsch CF-2s, for example, with my Kenwood -- yuck! In the case of the H/K, it would be hard to venture that it's the electronics -- but it still could be, if the speakers are as warm and laid back as the H/K tends to be.
My thought is, just what are you trying to do? You want it LOUD... you want to push above 115dB or something? Or, you just trying to get better sounds at a reasonable volume (80dB-90dB)?
I see you're using Polks R50s for your mains (FRONT: L/R). I don't have any problems with Polks. My apartment in Rhode Island has the Polk RTi28s for fronts matched with a Denon receiver. (My house in Florida is where my Paradigms are... where I'm sitting now... too cold in New England. Oh, sorry for this, but... Go Pats!)