Ascot Chang is more expensive than the off the rack suit store, but it offers a superior product that's worth the extra time and money. They have a full selection of styles and materials. Maybe it's not as much fun as getting a suit in Hong Kong yourself, (but at least you don't have to fly there.)
These Hong Kong tailors makes great made-to-measure shirts, suits, jackets and pants. There is a great range of fabrics from which to choose. They'll answer all your questions about collar styles, etc. Very classic timeless design.