One's idea of class usually differs from one person to the next. When people attempt to "dress classy" it's often difficult for them not to end up looking like a spiv!! If you have to ask such a question, you should probably give up. You don't want to look pretentious. lol
There are tons of awesome brands for men, you just have to think about the price your willing to pay.
Expensive: • Ralph Lauren (but it's maybe a bit too obvious, what really impresses me is when guys can find not so obvious brands and even cheaper brands and dress nicely/classy). • Acne Studios • Givenchy • Helmut Lang • Balmain
Medium to cheap: • Paul Smith • Zara (has the most good looking and cheap clothes you'll find in my opinion). • H&M • COS
I think it's really easy for a guy to dress classy or nicely, whether you have a lot of money or not. You just have to have an eye for things like that :)