Bobcox,
Some manufacturers might deliberately tweak amplfiers to color sound in a particular way (ex. attenuating high frequencies to make an amp sound "warm and easy-going"). Ian Masters wrote a great article on the subject at mastersonaudio.com. I would imagine such tweaking is common with companies like Arcam, whose amps have a "trademarked sound" to them. This isn't to say tweaking is always a "bad" thing...it just may account for a perceived difference between two products.
If you're shopping for an amp, just go to your local specialty store and ask to take a few amps (in your price range) home for an audition.
