While there will be differences in the actual specs for same class Denon and HK (and other brand name) A/V receivers, for the majority of people the difference in the sound won't be noticeable in isolation (and probably not even in an A/B comparison).
Even a power rating (assuming rms or continuous watts) of less than 50% is essentially insignificant (a 3 dB increase in loudness -- barely noticeable -- requires double (100% increase in) the power)
As long as you are buying a name brand you would be better considering the features the competing models offer. Number and type of inputs and outputs? Does it transcode audio and video? Does it have HDMI 1.2 or 1.3? The performance of the auto calibration mechanism? What audio decoders are present? etc. ... and of course, consider price, warranty and availability of local (or at least national) support.
To HK and Denon, I'd suggest you look at Yamaha, Pioneer Elite, Onyyo and NAD. Read reviews and pick on features not audio power and distortion ratings ... any receiver in the same class will be fine re. audio performance.
I know it's difficult to pick, but if you focus on features it's actually easier. Of course it helps if you define your needs first ... something you should do before considering any expensive consumer purchase. Some specific requirement you have may make or break a selection (For example, if you plan on 2 subwoofers, a model with two LFE outputs may be the right choice). On the other hand, it may come down to something minor like whether it's the same colour and width as other components, $50 cheaper, the way controls are laid out, or the number of assignable optical inputs ...!!).
Happy hunting.