What are the Ohm ratings? newbie

Whoa--don't confuse continuous power with "dynamic" power. They are very different things--and neither is terribly meaningful, frankly, the first because music isn't continuous and the second because there's no standard definition for it.

I'd say the NAD would likely give you more oomph. On the other hand, if the HK is working for you, you don't notice any distortion (and neither do your friends), and it doesn't seem to be running too hot, it's probably up to the job you're asking it to do. Basic rule for amps: If it sounds ok, it probably is.

No offense meant here, but, using an amp that isn't designed for lower impedances may offer one the opportunity to enjoy the sound while shortening the amps life, and maybe the speakers too. I've suggested this before, but the Spicas deserve a better amp. IMHO, a Forte 4 (a) would be worthy of consideration.

More about what the first guy said. He absolutely correct in all. But what needed to be mentioned is than audio signals introduces different impedance (ohms)right across the audio spectrum, simultaneously. If your amp isnt up to the job it will certainly be identifiable with speakers rated at 4ohms, since the current needed to maintain a signal and keep your amp stable is increased. A decent power supply will have no problem with 4 or 8 ohm speakers. a lousy power supply limits the bandwith and creates higher harmonic distortion (escpecially in the higher order 4th or 5th). This is where your power starts to go south. In short - if your are noticing this, than your in the market for a new amp.