That is going to depend on how you define better. There are people here who love Yamaha and will tell you the Arcam isn't better. There are people who will tell you the Arcam is definitely better because it's British, and it's not Yamaha.
You need to figure out what you mean by better. And you also need to decide if you want to get caught up in the endless game of constantly looking for something that's better than what you currently have. Look hard enough, long enough, and you will convince yourself that you have to upgrade.
2 things in your initial post are key. Your friend is adamant that he is right and you are not sure about your position. So you are already setting yourself up to hear what he is telling you to hear. It would be interesting to hear him tell you exactly which components in the Arcam are "better" than the Yamaha, and what tests/lab results he is basing this on?
You have a good receiver. Would I pay 75% more to get "maybe a touch better"? Only if I don't have to worry about what I am paying for my toys (which I do). If I didn't have to watch the HT budget, I am not sure an Arcam receiver would be my target.