Globetrotter: I think the question isn't as much dressing how you like, vs specific brands that may be appropriate, and I think there will be a bit of disagreement here. Obviously most of us aren't suggesting he go against the very clearly stated business formal dress code. There isn't any "over the top" about Brioni, unless you wear the tag on your sleeve that says "Brioni"
It's a clean, understated suit, that looks good, and if you wear it in a conservative color (charcoal, navy) you won't have any issues. I worked in IB and with several mutual funds for several years (including one of the most conservative, old-guard, MF companies) and wouldn't hesitate to wear Brioni, all day and every day, if it was an appropriate color/pattern. I think rsp was correct in saying that if you wear an appropriately colored/patterned brioni, 90-99% of people will not notice, or say "nice suit" at best, and the ones that do will be interested. When it comes to watches/accessories, a little more care must be taken to find items that are understated, but say you are wearing a $15k Patek, it is easy to say you received it from your father/grandfather, etc... I wore a daytona much of the time without issues, but I would recommend against something gaudy (14k/ss, gold, etc)