Well I reckon you're paying about 100 quid for the name when you buy a set of David Clarks - they are good, but are they 100 quid better than say Avcomm AC900's. I think not.
I'd happily recommend the Avcomm AC900 to anyone so consider them recommended!
They also have a Push To Talk which the David Clarks don't. This saves on an intercomm box if your a/c has a handheld mic.
Ya pays ya money, ya takes ya choice!
regards,
smithy.