Crusty, you're superbly placed to be able to compare these products.. And I assume you've spent a great deal of time and trouble selecting what is potentially the last power amp you'll ever have to buy. The Bryston should last a life time and I imagine you'll never have to make use of the 20 year warranty. My McIntosh is now 19 years old and has taken a beating, but it still sounds perfect.. Products of this quality last forever.
Arcam make top quality products which stand the test of time. But, their product range is truely lacking in top end amplification. Just picture the AV9 coupled to an array of Brystons... I'll bet you've even tried it out in your shop...