For money Quality which is better arcam or NAD?

Who knows? Six of one half a dozen of the other. "Better" is such an ambiguous term. YOU'd have to try both in YOUr system to get an answer that would satisfy YOU. Notice the emphasis on YOU?

Which is more reliable? You might want to try Consumer Reports for that answer.

In terms of reliability both brands have a good reputation so I think you are free to choose between them based on other criteria that are important to you like sound, features, looks, etc. I have owned both brands and never had any problems.

I'd pick the NAD. Personally I find the Arcam to be flat sounding.

Reliability-wise, I have owned an Arcam amp for about 2+ years before selling it to another user. After about a week the new owner called me to inform the transformer blew up.

Bizango...Rawr is NOT free to choose between them...he's bound by principle to be guided by our opinions and, unfortunately, I don't have one.