I've been offered an Arcam A85 in mint condition, would this be a better choice than my current Kandy K2?
I love my Roksan and wouldn't want to downgrade
Stick with your Roksan. Clearly you are smitten by it. The Arcam is a good amp but it is (in hi-fi terms) about 3 generations old. Not saying that newer is necessarily better but you have to factor in reliability, and the Arc might be a tad too laid back in its presentation. They are very similar in tonal qualities but the Kandy IMHO has a bit more bite.
Stick with a product you like and know.